diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index 94a25f7..35eb1dd 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>
\ No newline at end of file
diff --git a/src/main/java/org/operaton/fitpub/config/SecurityConfig.java b/src/main/java/org/operaton/fitpub/config/SecurityConfig.java
index ac2c3fb..49283f4 100644
--- a/src/main/java/org/operaton/fitpub/config/SecurityConfig.java
+++ b/src/main/java/org/operaton/fitpub/config/SecurityConfig.java
@@ -125,6 +125,9 @@ public class SecurityConfig {
                 // Protected endpoints - Batch Import API
                 .requestMatchers("/api/batch-import/**").authenticated()
 
+                // Protected endpoints - Privacy Zones API
+                .requestMatchers("/api/privacy-zones/**").authenticated()
+
                 // Protected endpoints - Activities API (upload, edit, delete)
                 .requestMatchers(HttpMethod.POST, "/api/activities/upload").authenticated()
                 .requestMatchers(HttpMethod.PUT, "/api/activities/*").authenticated()
diff --git a/src/main/java/org/operaton/fitpub/controller/ActivityController.java b/src/main/java/org/operaton/fitpub/controller/ActivityController.java
index 1432c20..c3c9378 100644
--- a/src/main/java/org/operaton/fitpub/controller/ActivityController.java
+++ b/src/main/java/org/operaton/fitpub/controller/ActivityController.java
@@ -7,6 +7,7 @@ import org.operaton.fitpub.model.dto.ActivityDTO;
 import org.operaton.fitpub.model.dto.ActivityUpdateRequest;
 import org.operaton.fitpub.model.dto.ActivityUploadRequest;
 import org.operaton.fitpub.model.entity.Activity;
+import org.operaton.fitpub.model.entity.PrivacyZone;
 import org.operaton.fitpub.model.entity.User;
 import org.operaton.fitpub.repository.UserRepository;
 import org.operaton.fitpub.service.ActivityFileService;
@@ -14,6 +15,8 @@ import org.operaton.fitpub.service.ActivityImageService;
 import org.operaton.fitpub.service.ActivityPostProcessingService;
 import org.operaton.fitpub.service.FederationService;
 import org.operaton.fitpub.service.FitFileService;
+import org.operaton.fitpub.service.PrivacyZoneService;
+import org.operaton.fitpub.service.TrackPrivacyFilter;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -44,6 +47,8 @@ public class ActivityController {
     private final FederationService federationService;
     private final ActivityImageService activityImageService;
     private final org.operaton.fitpub.service.WeatherService weatherService;
+    private final PrivacyZoneService privacyZoneService;
+    private final TrackPrivacyFilter trackPrivacyFilter;
 
     @Value("${fitpub.base-url}")
     private String baseUrl;
@@ -61,6 +66,23 @@ public class ActivityController {
         return user.getId();
     }
 
+    /**
+     * Helper method to get user ID from authenticated UserDetails, or null if not authenticated.
+     *
+     * @param userDetails the authenticated user details (may be null)
+     * @return the user's UUID, or null if not authenticated
+     */
+    private UUID getUserIdOrNull(UserDetails userDetails) {
+        if (userDetails == null) {
+            return null;
+        }
+        try {
+            return getUserId(userDetails);
+        } catch (UsernameNotFoundException e) {
+            return null;
+        }
+    }
+
     /**
      * Uploads an activity file (FIT or GPX) and creates a new activity.
      *
@@ -140,10 +162,21 @@ public class ActivityController {
             return ResponseEntity.notFound().build();
         }
 
+        // Get requesting user ID (or null for anonymous)
+        UUID requestingUserId = getUserIdOrNull(userDetails);
+
+        // Get activity owner's privacy zones
+        java.util.List<PrivacyZone> privacyZones = privacyZoneService.getActivePrivacyZones(activity.getUserId());
+
+        log.debug("Activity {} - Requesting user: {}, Owner: {}, Privacy zones: {}",
+                  id, requestingUserId, activity.getUserId(), privacyZones.size());
+
         // Check visibility
         if (activity.getVisibility() == Activity.Visibility.PUBLIC) {
-            // Public activities are always accessible
-            ActivityDTO dto = ActivityDTO.fromEntity(activity);
+            // Public activities are always accessible, but apply privacy filtering
+            ActivityDTO dto = ActivityDTO.fromEntityWithFiltering(activity, requestingUserId, privacyZones, trackPrivacyFilter);
+            log.debug("Activity {} - DTO privacy zones: {}", id,
+                      dto.getPrivacyZones() != null ? dto.getPrivacyZones().size() : 0);
             return ResponseEntity.ok(dto);
         }
 
@@ -160,7 +193,8 @@ public class ActivityController {
             return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
         }
 
-        ActivityDTO dto = ActivityDTO.fromEntity(checkedActivity);
+        // Apply privacy filtering (owner sees full track, others see filtered)
+        ActivityDTO dto = ActivityDTO.fromEntityWithFiltering(checkedActivity, requestingUserId, privacyZones, trackPrivacyFilter);
         return ResponseEntity.ok(dto);
     }
 
@@ -277,13 +311,15 @@ public class ActivityController {
      * @param username the username
      * @param page page number (default: 0)
      * @param size page size (default: 10)
+     * @param userDetails the authenticated user (optional)
      * @return page of public activities
      */
     @GetMapping("/user/{username}")
     public ResponseEntity<?> getUserPublicActivities(
         @PathVariable String username,
         @RequestParam(defaultValue = "0") int page,
-        @RequestParam(defaultValue = "10") int size
+        @RequestParam(defaultValue = "10") int size,
+        @AuthenticationPrincipal UserDetails userDetails
     ) {
         log.debug("Retrieving public activities for user: {}", username);
 
@@ -291,6 +327,12 @@ public class ActivityController {
         User user = userRepository.findByUsername(username)
             .orElseThrow(() -> new UsernameNotFoundException("User not found: " + username));
 
+        // Get requesting user ID (or null for anonymous)
+        UUID requestingUserId = getUserIdOrNull(userDetails);
+
+        // Get activity owner's privacy zones
+        java.util.List<PrivacyZone> privacyZones = privacyZoneService.getActivePrivacyZones(user.getId());
+
         // Get public activities only
         org.springframework.data.domain.Pageable pageable =
             org.springframework.data.domain.PageRequest.of(page, size,
@@ -299,8 +341,10 @@ public class ActivityController {
         org.springframework.data.domain.Page<Activity> activityPage =
             fitFileService.getPublicActivitiesByUserId(user.getId(), pageable);
 
-        // Convert to DTOs
-        org.springframework.data.domain.Page<ActivityDTO> dtoPage = activityPage.map(ActivityDTO::fromEntity);
+        // Convert to DTOs with privacy filtering
+        org.springframework.data.domain.Page<ActivityDTO> dtoPage = activityPage.map(activity ->
+            ActivityDTO.fromEntityWithFiltering(activity, requestingUserId, privacyZones, trackPrivacyFilter)
+        );
 
         return ResponseEntity.ok(dtoPage);
     }
@@ -343,8 +387,14 @@ public class ActivityController {
             }
         }
 
-        // Build GeoJSON FeatureCollection
-        ActivityDTO dto = ActivityDTO.fromEntity(activity);
+        // Get requesting user ID (or null for anonymous)
+        UUID requestingUserId = getUserIdOrNull(userDetails);
+
+        // Get activity owner's privacy zones
+        java.util.List<PrivacyZone> privacyZones = privacyZoneService.getActivePrivacyZones(activity.getUserId());
+
+        // Build GeoJSON FeatureCollection with privacy filtering
+        ActivityDTO dto = ActivityDTO.fromEntityWithFiltering(activity, requestingUserId, privacyZones, trackPrivacyFilter);
 
         // Use high-resolution track points if available, otherwise fall back to simplified track
         java.util.List<java.util.List<Double>> coordinates = new java.util.ArrayList<>();
diff --git a/src/main/java/org/operaton/fitpub/controller/PrivacyZoneController.java b/src/main/java/org/operaton/fitpub/controller/PrivacyZoneController.java
new file mode 100644
index 0000000..92d285b
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/controller/PrivacyZoneController.java
@@ -0,0 +1,185 @@
+package org.operaton.fitpub.controller;
+
+import jakarta.validation.Valid;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.operaton.fitpub.model.dto.CreatePrivacyZoneRequest;
+import org.operaton.fitpub.model.dto.PrivacyZoneDTO;
+import org.operaton.fitpub.model.dto.UpdatePrivacyZoneRequest;
+import org.operaton.fitpub.model.entity.PrivacyZone;
+import org.operaton.fitpub.model.entity.User;
+import org.operaton.fitpub.repository.UserRepository;
+import org.operaton.fitpub.service.PrivacyZoneService;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.core.userdetails.UsernameNotFoundException;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.stream.Collectors;
+
+/**
+ * REST controller for privacy zone management.
+ */
+@RestController
+@RequestMapping("/api/privacy-zones")
+@RequiredArgsConstructor
+@Slf4j
+public class PrivacyZoneController {
+
+    private final PrivacyZoneService privacyZoneService;
+    private final UserRepository userRepository;
+
+    /**
+     * Get all privacy zones for the authenticated user.
+     *
+     * @param userDetails the authenticated user
+     * @return list of privacy zones
+     */
+    @GetMapping
+    public ResponseEntity<List<PrivacyZoneDTO>> getPrivacyZones(@AuthenticationPrincipal UserDetails userDetails) {
+        log.debug("User {} retrieving privacy zones", userDetails.getUsername());
+
+        User user = userRepository.findByUsername(userDetails.getUsername())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+
+        List<PrivacyZone> zones = privacyZoneService.getUserPrivacyZones(user.getId());
+        List<PrivacyZoneDTO> zoneDTOs = zones.stream()
+            .map(PrivacyZoneDTO::fromEntity)
+            .collect(Collectors.toList());
+
+        return ResponseEntity.ok(zoneDTOs);
+    }
+
+    /**
+     * Create a new privacy zone.
+     *
+     * @param request the zone creation request
+     * @param userDetails the authenticated user
+     * @return created privacy zone
+     */
+    @PostMapping
+    public ResponseEntity<PrivacyZoneDTO> createPrivacyZone(
+        @Valid @RequestBody CreatePrivacyZoneRequest request,
+        @AuthenticationPrincipal UserDetails userDetails
+    ) {
+        log.info("User {} creating privacy zone: {}", userDetails.getUsername(), request.getName());
+
+        User user = userRepository.findByUsername(userDetails.getUsername())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+
+        PrivacyZone zone = privacyZoneService.createPrivacyZone(
+            user.getId(),
+            request.getName(),
+            request.getDescription(),
+            request.getLatitude(),
+            request.getLongitude(),
+            request.getRadiusMeters()
+        );
+
+        return ResponseEntity.status(HttpStatus.CREATED).body(PrivacyZoneDTO.fromEntity(zone));
+    }
+
+    /**
+     * Update an existing privacy zone.
+     *
+     * @param zoneId the zone ID
+     * @param request the update request
+     * @param userDetails the authenticated user
+     * @return updated privacy zone
+     */
+    @PutMapping("/{zoneId}")
+    public ResponseEntity<PrivacyZoneDTO> updatePrivacyZone(
+        @PathVariable UUID zoneId,
+        @Valid @RequestBody UpdatePrivacyZoneRequest request,
+        @AuthenticationPrincipal UserDetails userDetails
+    ) {
+        log.info("User {} updating privacy zone {}", userDetails.getUsername(), zoneId);
+
+        User user = userRepository.findByUsername(userDetails.getUsername())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+
+        try {
+            PrivacyZone zone = privacyZoneService.updatePrivacyZone(
+                zoneId,
+                user.getId(),
+                request.getName(),
+                request.getDescription(),
+                request.getLatitude(),
+                request.getLongitude(),
+                request.getRadiusMeters()
+            );
+
+            return ResponseEntity.ok(PrivacyZoneDTO.fromEntity(zone));
+        } catch (SecurityException e) {
+            return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
+        } catch (IllegalArgumentException e) {
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+
+    /**
+     * Toggle a privacy zone's active status.
+     *
+     * @param zoneId the zone ID
+     * @param body request body with isActive boolean
+     * @param userDetails the authenticated user
+     * @return updated privacy zone
+     */
+    @PatchMapping("/{zoneId}/toggle")
+    public ResponseEntity<PrivacyZoneDTO> togglePrivacyZone(
+        @PathVariable UUID zoneId,
+        @RequestBody Map<String, Boolean> body,
+        @AuthenticationPrincipal UserDetails userDetails
+    ) {
+        log.info("User {} toggling privacy zone {}", userDetails.getUsername(), zoneId);
+
+        User user = userRepository.findByUsername(userDetails.getUsername())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+
+        Boolean isActive = body.get("isActive");
+        if (isActive == null) {
+            return ResponseEntity.badRequest().build();
+        }
+
+        try {
+            PrivacyZone zone = privacyZoneService.togglePrivacyZone(zoneId, user.getId(), isActive);
+            return ResponseEntity.ok(PrivacyZoneDTO.fromEntity(zone));
+        } catch (SecurityException e) {
+            return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
+        } catch (IllegalArgumentException e) {
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+
+    /**
+     * Delete a privacy zone.
+     *
+     * @param zoneId the zone ID
+     * @param userDetails the authenticated user
+     * @return no content on success
+     */
+    @DeleteMapping("/{zoneId}")
+    public ResponseEntity<Void> deletePrivacyZone(
+        @PathVariable UUID zoneId,
+        @AuthenticationPrincipal UserDetails userDetails
+    ) {
+        log.info("User {} deleting privacy zone {}", userDetails.getUsername(), zoneId);
+
+        User user = userRepository.findByUsername(userDetails.getUsername())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+
+        try {
+            privacyZoneService.deletePrivacyZone(zoneId, user.getId());
+            return ResponseEntity.noContent().build();
+        } catch (SecurityException e) {
+            return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
+        } catch (IllegalArgumentException e) {
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+}
diff --git a/src/main/java/org/operaton/fitpub/model/dto/ActivityDTO.java b/src/main/java/org/operaton/fitpub/model/dto/ActivityDTO.java
index 53b99b8..e7328ba 100644
--- a/src/main/java/org/operaton/fitpub/model/dto/ActivityDTO.java
+++ b/src/main/java/org/operaton/fitpub/model/dto/ActivityDTO.java
@@ -9,6 +9,8 @@ import lombok.NoArgsConstructor;
 import org.locationtech.jts.geom.Coordinate;
 import org.locationtech.jts.geom.LineString;
 import org.operaton.fitpub.model.entity.Activity;
+import org.operaton.fitpub.model.entity.PrivacyZone;
+import org.operaton.fitpub.service.TrackPrivacyFilter;
 import org.operaton.fitpub.util.ActivityFormatter;
 
 import java.math.BigDecimal;
@@ -57,6 +59,9 @@ public class ActivityDTO {
     private Long commentsCount;
     private Boolean likedByCurrentUser; // True if current user has liked this activity
 
+    // Privacy zones (only for activity owner, to show what's hidden for others)
+    private List<PrivacyZonePreview> privacyZones;
+
     // Convenience getters for flattened metrics (for frontend compatibility)
     public Integer getAverageHeartRate() {
         return metrics != null ? metrics.getAverageHeartRate() : null;
@@ -139,6 +144,124 @@ public class ActivityDTO {
         return builder.build();
     }
 
+    /**
+     * Creates a DTO from an Activity entity with privacy zone filtering applied.
+     * Filters GPS coordinates that fall within the activity owner's privacy zones.
+     *
+     * @param activity the activity entity
+     * @param requestingUserId the ID of the user requesting the activity (null for anonymous)
+     * @param privacyZones the activity owner's active privacy zones
+     * @param filter the privacy filter service
+     * @return activity DTO with filtered GPS data, or null if entire track was filtered
+     */
+    public static ActivityDTO fromEntityWithFiltering(
+        Activity activity,
+        UUID requestingUserId,
+        List<PrivacyZone> privacyZones,
+        TrackPrivacyFilter filter
+    ) {
+        // If requester is the activity owner, don't filter (show full track)
+        boolean isOwner = requestingUserId != null && requestingUserId.equals(activity.getUserId());
+
+        // If no privacy zones or requester is owner, use standard conversion
+        if (privacyZones == null || privacyZones.isEmpty() || isOwner) {
+            if (isOwner && privacyZones != null && !privacyZones.isEmpty()) {
+                org.slf4j.LoggerFactory.getLogger(ActivityDTO.class)
+                    .info("Activity {} - Owner viewing, bypassing {} privacy zones",
+                          activity.getId(), privacyZones.size());
+
+                // For owner, return full track but include privacy zones for visualization
+                ActivityDTO dto = fromEntity(activity);
+                dto.setPrivacyZones(privacyZones.stream()
+                    .map(zone -> PrivacyZonePreview.builder()
+                        .id(zone.getId())
+                        .name(zone.getName())
+                        .latitude(zone.getCenterPoint().getY())
+                        .longitude(zone.getCenterPoint().getX())
+                        .radiusMeters(zone.getRadiusMeters())
+                        .build())
+                    .collect(java.util.stream.Collectors.toList()));
+                return dto;
+            }
+            return fromEntity(activity);
+        }
+
+        // Apply filtering to tracks
+        LineString filteredSimplifiedTrack = null;
+        String filteredTrackPointsJson = null;
+
+        if (activity.getSimplifiedTrack() != null) {
+            filteredSimplifiedTrack = filter.filterLineString(activity.getSimplifiedTrack(), privacyZones);
+        }
+
+        if (activity.getTrackPointsJson() != null && !activity.getTrackPointsJson().isEmpty()) {
+            filteredTrackPointsJson = filter.filterTrackPointsJson(activity.getTrackPointsJson(), privacyZones);
+        }
+
+        // If entire track was filtered out, return null (activity is completely private)
+        if (filteredSimplifiedTrack == null && filteredTrackPointsJson == null) {
+            // Return basic activity info without GPS data
+            return ActivityDTO.builder()
+                .id(activity.getId())
+                .userId(activity.getUserId())
+                .activityType(ActivityFormatter.formatActivityType(activity.getActivityType()))
+                .title(activity.getTitle())
+                .description(activity.getDescription())
+                .startedAt(activity.getStartedAt())
+                .endedAt(activity.getEndedAt())
+                .timezone(activity.getTimezone())
+                .visibility(activity.getVisibility().name())
+                .totalDistance(activity.getTotalDistance())
+                .totalDurationSeconds(activity.getTotalDurationSeconds())
+                .elevationGain(activity.getElevationGain())
+                .elevationLoss(activity.getElevationLoss())
+                .metrics(activity.getMetrics() != null ? ActivityMetricsDTO.fromEntity(activity.getMetrics()) : null)
+                .createdAt(activity.getCreatedAt())
+                .updatedAt(activity.getUpdatedAt())
+                .hasGpsTrack(false) // Mark as no GPS data available
+                .build();
+        }
+
+        // Build DTO with filtered tracks
+        ActivityDTOBuilder builder = ActivityDTO.builder()
+            .id(activity.getId())
+            .userId(activity.getUserId())
+            .activityType(ActivityFormatter.formatActivityType(activity.getActivityType()))
+            .title(activity.getTitle())
+            .description(activity.getDescription())
+            .startedAt(activity.getStartedAt())
+            .endedAt(activity.getEndedAt())
+            .timezone(activity.getTimezone())
+            .visibility(activity.getVisibility().name())
+            .totalDistance(activity.getTotalDistance())
+            .elevationGain(activity.getElevationGain())
+            .elevationLoss(activity.getElevationLoss())
+            .createdAt(activity.getCreatedAt())
+            .updatedAt(activity.getUpdatedAt());
+
+        if (activity.getTotalDurationSeconds() != null) {
+            builder.totalDurationSeconds(activity.getTotalDurationSeconds());
+        }
+
+        if (activity.getMetrics() != null) {
+            builder.metrics(ActivityMetricsDTO.fromEntity(activity.getMetrics()));
+        }
+
+        // Add filtered GPS data
+        boolean hasGps = filteredSimplifiedTrack != null;
+        builder.hasGpsTrack(hasGps);
+
+        if (hasGps) {
+            builder.simplifiedTrack(lineStringToGeoJson(filteredSimplifiedTrack));
+        }
+
+        if (filteredTrackPointsJson != null) {
+            builder.trackPoints(parseTrackPoints(filteredTrackPointsJson));
+        }
+
+        return builder.build();
+    }
+
     /**
      * Converts a JTS LineString to GeoJSON format.
      */
@@ -187,4 +310,19 @@ public class ActivityDTO {
         }
         return null;
     }
+
+    /**
+     * Simple preview of a privacy zone for map rendering.
+     */
+    @Data
+    @Builder
+    @NoArgsConstructor
+    @AllArgsConstructor
+    public static class PrivacyZonePreview {
+        private UUID id;
+        private String name;
+        private Double latitude;
+        private Double longitude;
+        private Integer radiusMeters;
+    }
 }
diff --git a/src/main/java/org/operaton/fitpub/model/dto/CreatePrivacyZoneRequest.java b/src/main/java/org/operaton/fitpub/model/dto/CreatePrivacyZoneRequest.java
new file mode 100644
index 0000000..5b27bca
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/model/dto/CreatePrivacyZoneRequest.java
@@ -0,0 +1,39 @@
+package org.operaton.fitpub.model.dto;
+
+import jakarta.validation.constraints.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * Request DTO for creating a new privacy zone.
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class CreatePrivacyZoneRequest {
+
+    @NotNull(message = "Name is required")
+    @Size(min = 1, max = 100, message = "Name must be between 1 and 100 characters")
+    private String name;
+
+    @Size(max = 500, message = "Description must not exceed 500 characters")
+    private String description;
+
+    @NotNull(message = "Latitude is required")
+    @DecimalMin(value = "-90.0", message = "Latitude must be between -90 and 90")
+    @DecimalMax(value = "90.0", message = "Latitude must be between -90 and 90")
+    private Double latitude;
+
+    @NotNull(message = "Longitude is required")
+    @DecimalMin(value = "-180.0", message = "Longitude must be between -180 and 180")
+    @DecimalMax(value = "180.0", message = "Longitude must be between -180 and 180")
+    private Double longitude;
+
+    @NotNull(message = "Radius is required")
+    @Min(value = 50, message = "Radius must be at least 50 meters")
+    @Max(value = 10000, message = "Radius must not exceed 10000 meters (10 km)")
+    private Integer radiusMeters;
+}
diff --git a/src/main/java/org/operaton/fitpub/model/dto/PrivacyZoneDTO.java b/src/main/java/org/operaton/fitpub/model/dto/PrivacyZoneDTO.java
new file mode 100644
index 0000000..2571867
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/model/dto/PrivacyZoneDTO.java
@@ -0,0 +1,51 @@
+package org.operaton.fitpub.model.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.operaton.fitpub.model.entity.PrivacyZone;
+
+import java.time.LocalDateTime;
+import java.util.UUID;
+
+/**
+ * DTO for PrivacyZone data transfer.
+ * Returns lat/lon as separate fields extracted from PostGIS Point geometry.
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class PrivacyZoneDTO {
+
+    private UUID id;
+    private UUID userId;
+    private String name;
+    private String description;
+    private Double latitude;
+    private Double longitude;
+    private Integer radiusMeters;
+    private Boolean isActive;
+    private LocalDateTime createdAt;
+    private LocalDateTime updatedAt;
+
+    /**
+     * Creates a DTO from a PrivacyZone entity.
+     * Extracts latitude and longitude from PostGIS Point geometry.
+     */
+    public static PrivacyZoneDTO fromEntity(PrivacyZone zone) {
+        return PrivacyZoneDTO.builder()
+            .id(zone.getId())
+            .userId(zone.getUserId())
+            .name(zone.getName())
+            .description(zone.getDescription())
+            .latitude(zone.getCenterPoint().getY())
+            .longitude(zone.getCenterPoint().getX())
+            .radiusMeters(zone.getRadiusMeters())
+            .isActive(zone.getIsActive())
+            .createdAt(zone.getCreatedAt())
+            .updatedAt(zone.getUpdatedAt())
+            .build();
+    }
+}
diff --git a/src/main/java/org/operaton/fitpub/model/dto/UpdatePrivacyZoneRequest.java b/src/main/java/org/operaton/fitpub/model/dto/UpdatePrivacyZoneRequest.java
new file mode 100644
index 0000000..babc611
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/model/dto/UpdatePrivacyZoneRequest.java
@@ -0,0 +1,40 @@
+package org.operaton.fitpub.model.dto;
+
+import jakarta.validation.constraints.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * Request DTO for updating an existing privacy zone.
+ * All fields are required (full update).
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class UpdatePrivacyZoneRequest {
+
+    @NotNull(message = "Name is required")
+    @Size(min = 1, max = 100, message = "Name must be between 1 and 100 characters")
+    private String name;
+
+    @Size(max = 500, message = "Description must not exceed 500 characters")
+    private String description;
+
+    @NotNull(message = "Latitude is required")
+    @DecimalMin(value = "-90.0", message = "Latitude must be between -90 and 90")
+    @DecimalMax(value = "90.0", message = "Latitude must be between -90 and 90")
+    private Double latitude;
+
+    @NotNull(message = "Longitude is required")
+    @DecimalMin(value = "-180.0", message = "Longitude must be between -180 and 180")
+    @DecimalMax(value = "180.0", message = "Longitude must be between -180 and 180")
+    private Double longitude;
+
+    @NotNull(message = "Radius is required")
+    @Min(value = 50, message = "Radius must be at least 50 meters")
+    @Max(value = 10000, message = "Radius must not exceed 10000 meters (10 km)")
+    private Integer radiusMeters;
+}
diff --git a/src/main/java/org/operaton/fitpub/model/entity/PrivacyZone.java b/src/main/java/org/operaton/fitpub/model/entity/PrivacyZone.java
new file mode 100644
index 0000000..c751e1b
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/model/entity/PrivacyZone.java
@@ -0,0 +1,70 @@
+package org.operaton.fitpub.model.entity;
+
+import jakarta.persistence.*;
+import lombok.*;
+import org.hibernate.annotations.CreationTimestamp;
+import org.hibernate.annotations.UpdateTimestamp;
+import org.locationtech.jts.geom.Point;
+
+import java.time.LocalDateTime;
+import java.util.UUID;
+
+/**
+ * Entity representing a user-defined privacy zone for GPS track filtering.
+ * When activities pass through privacy zones, GPS coordinates within the zone are removed.
+ */
+@Entity
+@Table(name = "privacy_zones", indexes = {
+    @Index(name = "idx_privacy_zones_user", columnList = "user_id, is_active"),
+    @Index(name = "idx_privacy_zones_center_point", columnList = "center_point")
+})
+@Getter
+@Setter
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class PrivacyZone {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    private UUID id;
+
+    @Column(name = "user_id", nullable = false)
+    private UUID userId;
+
+    @Column(nullable = false, length = 100)
+    private String name;
+
+    @Column(columnDefinition = "TEXT")
+    private String description;
+
+    /**
+     * True center point of the privacy zone (PostGIS Point geometry).
+     * This is NOT the randomized display center shown in the UI.
+     */
+    @Column(name = "center_point", columnDefinition = "geometry(Point, 4326)", nullable = false)
+    private Point centerPoint;
+
+    /**
+     * Radius of the privacy zone in meters.
+     * All GPS points within this distance from centerPoint will be filtered.
+     */
+    @Column(name = "radius_meters", nullable = false)
+    private Integer radiusMeters;
+
+    /**
+     * Whether this privacy zone is currently active.
+     * Inactive zones are ignored during filtering.
+     */
+    @Column(name = "is_active", nullable = false)
+    @Builder.Default
+    private Boolean isActive = true;
+
+    @CreationTimestamp
+    @Column(name = "created_at", nullable = false, updatable = false)
+    private LocalDateTime createdAt;
+
+    @UpdateTimestamp
+    @Column(name = "updated_at", nullable = false)
+    private LocalDateTime updatedAt;
+}
diff --git a/src/main/java/org/operaton/fitpub/repository/PrivacyZoneRepository.java b/src/main/java/org/operaton/fitpub/repository/PrivacyZoneRepository.java
new file mode 100644
index 0000000..95ce0d1
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/repository/PrivacyZoneRepository.java
@@ -0,0 +1,89 @@
+package org.operaton.fitpub.repository;
+
+import org.operaton.fitpub.model.entity.PrivacyZone;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * Repository for PrivacyZone entities.
+ */
+@Repository
+public interface PrivacyZoneRepository extends JpaRepository<PrivacyZone, UUID> {
+
+    /**
+     * Find all active privacy zones for a user.
+     *
+     * @param userId the user ID
+     * @return list of active privacy zones
+     */
+    List<PrivacyZone> findByUserIdAndIsActiveTrue(UUID userId);
+
+    /**
+     * Find all privacy zones for a user (including inactive).
+     *
+     * @param userId the user ID
+     * @return list of all privacy zones
+     */
+    List<PrivacyZone> findByUserIdOrderByCreatedAtDesc(UUID userId);
+
+    /**
+     * Check if a point falls within any of the user's active privacy zones.
+     * Uses PostGIS ST_DWithin for efficient radius-based spatial queries.
+     *
+     * @param userId the user ID
+     * @param latitude the point latitude
+     * @param longitude the point longitude
+     * @return true if point is within any privacy zone
+     */
+    @Query(value = "SELECT EXISTS(" +
+                   "SELECT 1 FROM privacy_zones " +
+                   "WHERE user_id = :userId " +
+                   "AND is_active = TRUE " +
+                   "AND ST_DWithin(" +
+                   "    center_point::geography, " +
+                   "    ST_SetSRID(ST_MakePoint(:longitude, :latitude), 4326)::geography, " +
+                   "    radius_meters" +
+                   ")" +
+                   ")", nativeQuery = true)
+    boolean isPointInAnyZone(
+        @Param("userId") UUID userId,
+        @Param("latitude") double latitude,
+        @Param("longitude") double longitude
+    );
+
+    /**
+     * Find all privacy zones that a point falls within.
+     * Returns the actual zones (not just boolean) for detailed filtering.
+     *
+     * @param userId the user ID
+     * @param latitude the point latitude
+     * @param longitude the point longitude
+     * @return list of privacy zones containing this point
+     */
+    @Query(value = "SELECT * FROM privacy_zones " +
+                   "WHERE user_id = :userId " +
+                   "AND is_active = TRUE " +
+                   "AND ST_DWithin(" +
+                   "    center_point::geography, " +
+                   "    ST_SetSRID(ST_MakePoint(:longitude, :latitude), 4326)::geography, " +
+                   "    radius_meters" +
+                   ")", nativeQuery = true)
+    List<PrivacyZone> findZonesContainingPoint(
+        @Param("userId") UUID userId,
+        @Param("latitude") double latitude,
+        @Param("longitude") double longitude
+    );
+
+    /**
+     * Count active privacy zones for a user.
+     *
+     * @param userId the user ID
+     * @return count of active zones
+     */
+    long countByUserIdAndIsActiveTrue(UUID userId);
+}
diff --git a/src/main/java/org/operaton/fitpub/service/ActivityImageService.java b/src/main/java/org/operaton/fitpub/service/ActivityImageService.java
index eb6a5b5..e151fe4 100644
--- a/src/main/java/org/operaton/fitpub/service/ActivityImageService.java
+++ b/src/main/java/org/operaton/fitpub/service/ActivityImageService.java
@@ -2,7 +2,9 @@ package org.operaton.fitpub.service;
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.locationtech.jts.geom.LineString;
 import org.operaton.fitpub.model.entity.Activity;
+import org.operaton.fitpub.model.entity.PrivacyZone;
 import org.operaton.fitpub.util.ActivityFormatter;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;
@@ -26,6 +28,8 @@ import java.util.UUID;
 public class ActivityImageService {
 
     private final OsmTileRenderer osmTileRenderer;
+    private final PrivacyZoneService privacyZoneService;
+    private final TrackPrivacyFilter trackPrivacyFilter;
 
     @Value("${fitpub.storage.images.path:${java.io.tmpdir}/fitpub/images}")
     private String imagesPath;
@@ -38,12 +42,16 @@ public class ActivityImageService {
 
     /**
      * Generate a preview image for an activity showing the track outline and metadata.
+     * Applies privacy zone filtering to ensure GPS coordinates within zones are not rendered.
      *
      * @param activity the activity to generate an image for
      * @return the URL of the generated image
      */
     public String generateActivityImage(Activity activity) {
         try {
+            // Apply privacy zone filtering before rendering
+            Activity filteredActivity = applyPrivacyFiltering(activity);
+
             // Image dimensions
             int width = 1200;
             int height = 630; // Open Graph standard size
@@ -59,11 +67,11 @@ public class ActivityImageService {
 
             // Calculate bounds once for both map tiles and track rendering
             TrackBounds trackBounds = null;
-            boolean isIndoorActivity = activity.getSimplifiedTrack() == null;
+            boolean isIndoorActivity = filteredActivity.getSimplifiedTrack() == null;
 
             // Render background - either OSM tiles or gradient background
-            if (activity.getTrackPointsJson() != null && !activity.getTrackPointsJson().isEmpty()) {
-                trackBounds = calculateTrackBounds(activity);
+            if (filteredActivity.getTrackPointsJson() != null && !filteredActivity.getTrackPointsJson().isEmpty()) {
+                trackBounds = calculateTrackBounds(filteredActivity);
             }
 
             if (osmTilesEnabled && trackBounds != null && !isIndoorActivity) {
@@ -107,20 +115,20 @@ public class ActivityImageService {
 
                 // For indoor activities, draw a large emoji in the center-left area
                 if (isIndoorActivity) {
-                    drawIndoorActivityEmoji(g2d, activity, width, height);
+                    drawIndoorActivityEmoji(g2d, filteredActivity, width, height);
                 }
             }
 
             // Draw track if available (not for indoor activities)
             if (!isIndoorActivity) {
-                if (activity.getTrackPointsJson() != null && !activity.getTrackPointsJson().isEmpty()) {
-                    drawTrack(g2d, activity, width, height);
-                } else if (activity.getSimplifiedTrack() != null) {
-                    drawSimplifiedTrack(g2d, activity, width, height);
+                if (filteredActivity.getTrackPointsJson() != null && !filteredActivity.getTrackPointsJson().isEmpty()) {
+                    drawTrack(g2d, filteredActivity, width, height);
+                } else if (filteredActivity.getSimplifiedTrack() != null) {
+                    drawSimplifiedTrack(g2d, filteredActivity, width, height);
                 }
             }
 
-            // Draw metadata overlay
+            // Draw metadata overlay (use original activity for metadata, not filtered)
             drawMetadata(g2d, activity, width, height, isIndoorActivity);
 
             g2d.dispose();
@@ -741,6 +749,63 @@ public class ActivityImageService {
         g2d.drawString(emoji, emojiX - emojiWidth / 2, emojiY + emojiHeight / 3);
     }
 
+    /**
+     * Apply privacy zone filtering to an activity's GPS data.
+     * Filters both simplified track and full track points JSON.
+     *
+     * @param activity the original activity
+     * @return a copy of the activity with filtered GPS data
+     */
+    private Activity applyPrivacyFiltering(Activity activity) {
+        // Get user's active privacy zones
+        List<PrivacyZone> privacyZones = privacyZoneService.getActivePrivacyZones(activity.getUserId());
+
+        // If no privacy zones, return original activity
+        if (privacyZones == null || privacyZones.isEmpty()) {
+            return activity;
+        }
+
+        // Create a copy of the activity with filtered tracks
+        Activity filtered = new Activity();
+        filtered.setId(activity.getId());
+        filtered.setUserId(activity.getUserId());
+        filtered.setActivityType(activity.getActivityType());
+        filtered.setTitle(activity.getTitle());
+        filtered.setDescription(activity.getDescription());
+        filtered.setStartedAt(activity.getStartedAt());
+        filtered.setEndedAt(activity.getEndedAt());
+        filtered.setTimezone(activity.getTimezone());
+        filtered.setVisibility(activity.getVisibility());
+        filtered.setTotalDistance(activity.getTotalDistance());
+        filtered.setTotalDurationSeconds(activity.getTotalDurationSeconds());
+        filtered.setElevationGain(activity.getElevationGain());
+        filtered.setElevationLoss(activity.getElevationLoss());
+        filtered.setMetrics(activity.getMetrics());
+        filtered.setCreatedAt(activity.getCreatedAt());
+        filtered.setUpdatedAt(activity.getUpdatedAt());
+
+        // Filter simplified track
+        if (activity.getSimplifiedTrack() != null) {
+            LineString filteredTrack = trackPrivacyFilter.filterLineString(
+                activity.getSimplifiedTrack(),
+                privacyZones
+            );
+            filtered.setSimplifiedTrack(filteredTrack);
+        }
+
+        // Filter track points JSON
+        if (activity.getTrackPointsJson() != null && !activity.getTrackPointsJson().isEmpty()) {
+            String filteredJson = trackPrivacyFilter.filterTrackPointsJson(
+                activity.getTrackPointsJson(),
+                privacyZones
+            );
+            filtered.setTrackPointsJson(filteredJson);
+        }
+
+        log.debug("Applied privacy filtering to activity {} for image generation", activity.getId());
+        return filtered;
+    }
+
     /**
      * Helper class to store track geographic bounds.
      */
diff --git a/src/main/java/org/operaton/fitpub/service/PrivacyZoneService.java b/src/main/java/org/operaton/fitpub/service/PrivacyZoneService.java
new file mode 100644
index 0000000..0965e0a
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/service/PrivacyZoneService.java
@@ -0,0 +1,196 @@
+package org.operaton.fitpub.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.geom.Point;
+import org.locationtech.jts.geom.PrecisionModel;
+import org.operaton.fitpub.model.entity.PrivacyZone;
+import org.operaton.fitpub.repository.PrivacyZoneRepository;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * Service for managing GPS privacy zones.
+ */
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class PrivacyZoneService {
+
+    private final PrivacyZoneRepository privacyZoneRepository;
+
+    private static final int SRID = 4326; // WGS84
+    private final GeometryFactory geometryFactory = new GeometryFactory(new PrecisionModel(), SRID);
+
+    /**
+     * Create a new privacy zone for a user.
+     *
+     * @param userId user ID
+     * @param name zone name
+     * @param description zone description (optional)
+     * @param latitude center latitude
+     * @param longitude center longitude
+     * @param radiusMeters radius in meters
+     * @return created privacy zone
+     */
+    @Transactional
+    public PrivacyZone createPrivacyZone(
+        UUID userId,
+        String name,
+        String description,
+        double latitude,
+        double longitude,
+        int radiusMeters
+    ) {
+        log.info("Creating privacy zone for user {} at ({}, {}) with radius {}m",
+                 userId, latitude, longitude, radiusMeters);
+
+        // Validate inputs
+        if (radiusMeters <= 0 || radiusMeters > 10000) {
+            throw new IllegalArgumentException("Radius must be between 1 and 10000 meters");
+        }
+        if (latitude < -90 || latitude > 90) {
+            throw new IllegalArgumentException("Invalid latitude");
+        }
+        if (longitude < -180 || longitude > 180) {
+            throw new IllegalArgumentException("Invalid longitude");
+        }
+
+        Point centerPoint = geometryFactory.createPoint(new Coordinate(longitude, latitude));
+
+        PrivacyZone zone = PrivacyZone.builder()
+            .userId(userId)
+            .name(name)
+            .description(description)
+            .centerPoint(centerPoint)
+            .radiusMeters(radiusMeters)
+            .isActive(true)
+            .build();
+
+        return privacyZoneRepository.save(zone);
+    }
+
+    /**
+     * Get all privacy zones for a user (active and inactive).
+     *
+     * @param userId user ID
+     * @return list of privacy zones
+     */
+    @Transactional(readOnly = true)
+    public List<PrivacyZone> getUserPrivacyZones(UUID userId) {
+        return privacyZoneRepository.findByUserIdOrderByCreatedAtDesc(userId);
+    }
+
+    /**
+     * Get all active privacy zones for a user.
+     *
+     * @param userId user ID
+     * @return list of active privacy zones
+     */
+    @Transactional(readOnly = true)
+    public List<PrivacyZone> getActivePrivacyZones(UUID userId) {
+        return privacyZoneRepository.findByUserIdAndIsActiveTrue(userId);
+    }
+
+    /**
+     * Update a privacy zone.
+     *
+     * @param zoneId zone ID
+     * @param userId user ID (for authorization)
+     * @param name new name
+     * @param description new description
+     * @param latitude new latitude
+     * @param longitude new longitude
+     * @param radiusMeters new radius
+     * @return updated privacy zone
+     */
+    @Transactional
+    public PrivacyZone updatePrivacyZone(
+        UUID zoneId,
+        UUID userId,
+        String name,
+        String description,
+        double latitude,
+        double longitude,
+        int radiusMeters
+    ) {
+        PrivacyZone zone = privacyZoneRepository.findById(zoneId)
+            .orElseThrow(() -> new IllegalArgumentException("Privacy zone not found"));
+
+        if (!zone.getUserId().equals(userId)) {
+            throw new SecurityException("Not authorized to update this privacy zone");
+        }
+
+        // Validate
+        if (radiusMeters <= 0 || radiusMeters > 10000) {
+            throw new IllegalArgumentException("Radius must be between 1 and 10000 meters");
+        }
+
+        Point centerPoint = geometryFactory.createPoint(new Coordinate(longitude, latitude));
+
+        zone.setName(name);
+        zone.setDescription(description);
+        zone.setCenterPoint(centerPoint);
+        zone.setRadiusMeters(radiusMeters);
+
+        return privacyZoneRepository.save(zone);
+    }
+
+    /**
+     * Toggle a privacy zone's active status.
+     *
+     * @param zoneId zone ID
+     * @param userId user ID (for authorization)
+     * @param isActive new active status
+     * @return updated privacy zone
+     */
+    @Transactional
+    public PrivacyZone togglePrivacyZone(UUID zoneId, UUID userId, boolean isActive) {
+        PrivacyZone zone = privacyZoneRepository.findById(zoneId)
+            .orElseThrow(() -> new IllegalArgumentException("Privacy zone not found"));
+
+        if (!zone.getUserId().equals(userId)) {
+            throw new SecurityException("Not authorized to update this privacy zone");
+        }
+
+        zone.setIsActive(isActive);
+        return privacyZoneRepository.save(zone);
+    }
+
+    /**
+     * Delete a privacy zone.
+     *
+     * @param zoneId zone ID
+     * @param userId user ID (for authorization)
+     */
+    @Transactional
+    public void deletePrivacyZone(UUID zoneId, UUID userId) {
+        PrivacyZone zone = privacyZoneRepository.findById(zoneId)
+            .orElseThrow(() -> new IllegalArgumentException("Privacy zone not found"));
+
+        if (!zone.getUserId().equals(userId)) {
+            throw new SecurityException("Not authorized to delete this privacy zone");
+        }
+
+        privacyZoneRepository.delete(zone);
+        log.info("Deleted privacy zone {} for user {}", zoneId, userId);
+    }
+
+    /**
+     * Check if a GPS point falls within any of the user's active privacy zones.
+     *
+     * @param userId user ID
+     * @param latitude point latitude
+     * @param longitude point longitude
+     * @return true if point is within any active privacy zone
+     */
+    @Transactional(readOnly = true)
+    public boolean isPointInPrivacyZone(UUID userId, double latitude, double longitude) {
+        return privacyZoneRepository.isPointInAnyZone(userId, latitude, longitude);
+    }
+}
diff --git a/src/main/java/org/operaton/fitpub/service/TrackPrivacyFilter.java b/src/main/java/org/operaton/fitpub/service/TrackPrivacyFilter.java
new file mode 100644
index 0000000..fc9ed03
--- /dev/null
+++ b/src/main/java/org/operaton/fitpub/service/TrackPrivacyFilter.java
@@ -0,0 +1,218 @@
+package org.operaton.fitpub.service;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.geom.LineString;
+import org.locationtech.jts.geom.Point;
+import org.locationtech.jts.geom.PrecisionModel;
+import org.operaton.fitpub.model.entity.PrivacyZone;
+import org.springframework.stereotype.Service;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.UUID;
+
+/**
+ * Service for filtering GPS tracks through privacy zones.
+ * Removes coordinates that fall within user-defined privacy zones.
+ */
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class TrackPrivacyFilter {
+
+    private static final int SRID = 4326; // WGS84
+    private final GeometryFactory geometryFactory = new GeometryFactory(new PrecisionModel(), SRID);
+    private final ObjectMapper objectMapper;
+
+    /**
+     * Filters a LineString track by removing coordinates within privacy zones.
+     *
+     * @param track the simplified track LineString
+     * @param zones list of active privacy zones
+     * @return filtered LineString, or null if <2 points remain
+     */
+    public LineString filterLineString(LineString track, List<PrivacyZone> zones) {
+        if (track == null || zones == null || zones.isEmpty()) {
+            return track;
+        }
+
+        List<Coordinate> filteredCoords = new ArrayList<>();
+        Coordinate[] coordinates = track.getCoordinates();
+        int originalCount = coordinates.length;
+        int filteredCount = 0;
+
+        for (Coordinate coord : coordinates) {
+            double latitude = coord.y;
+            double longitude = coord.x;
+
+            if (!isPointInAnyZone(latitude, longitude, zones)) {
+                filteredCoords.add(coord);
+            } else {
+                filteredCount++;
+            }
+        }
+
+        log.info("Privacy filter: {} zones active, {}/{} points filtered out",
+                 zones.size(), filteredCount, originalCount);
+
+        // Return null if track is completely filtered or too few points remain
+        if (filteredCoords.size() < 2) {
+            log.warn("Track completely filtered by privacy zones (or <2 points remain)");
+            return null;
+        }
+
+        return geometryFactory.createLineString(filteredCoords.toArray(new Coordinate[0]));
+    }
+
+    /**
+     * Filters track points JSON by removing points within privacy zones.
+     *
+     * @param trackPointsJson JSONB string containing track points
+     * @param zones list of active privacy zones
+     * @return filtered JSON string, or null if <2 points remain
+     */
+    public String filterTrackPointsJson(String trackPointsJson, List<PrivacyZone> zones) {
+        if (trackPointsJson == null || zones == null || zones.isEmpty()) {
+            return trackPointsJson;
+        }
+
+        try {
+            JsonNode root = objectMapper.readTree(trackPointsJson);
+
+            if (!root.isArray()) {
+                log.warn("Track points JSON is not an array");
+                return trackPointsJson;
+            }
+
+            ArrayNode filteredArray = objectMapper.createArrayNode();
+
+            for (JsonNode node : root) {
+                if (!node.has("latitude") || !node.has("longitude")) {
+                    continue; // Skip points without coordinates
+                }
+
+                double latitude = node.get("latitude").asDouble();
+                double longitude = node.get("longitude").asDouble();
+
+                if (!isPointInAnyZone(latitude, longitude, zones)) {
+                    filteredArray.add(node);
+                }
+            }
+
+            // Return null if track is completely filtered or too few points remain
+            if (filteredArray.size() < 2) {
+                log.debug("Track points completely filtered by privacy zones (or <2 points remain)");
+                return null;
+            }
+
+            return objectMapper.writeValueAsString(filteredArray);
+
+        } catch (Exception e) {
+            log.error("Error filtering track points JSON", e);
+            return trackPointsJson; // Return original on error (fail-open for owner)
+        }
+    }
+
+    /**
+     * Check if a point falls within any of the given privacy zones.
+     *
+     * @param latitude point latitude
+     * @param longitude point longitude
+     * @param zones list of privacy zones
+     * @return true if point is within any zone
+     */
+    private boolean isPointInAnyZone(double latitude, double longitude, List<PrivacyZone> zones) {
+        for (PrivacyZone zone : zones) {
+            Point center = zone.getCenterPoint();
+            double centerLat = center.getY();
+            double centerLon = center.getX();
+            int radiusMeters = zone.getRadiusMeters();
+
+            double distanceMeters = haversineDistance(latitude, longitude, centerLat, centerLon);
+
+            if (distanceMeters <= radiusMeters) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Calculate Haversine distance between two GPS coordinates.
+     * Returns distance in meters.
+     *
+     * @param lat1 first point latitude
+     * @param lon1 first point longitude
+     * @param lat2 second point latitude
+     * @param lon2 second point longitude
+     * @return distance in meters
+     */
+    private double haversineDistance(double lat1, double lon1, double lat2, double lon2) {
+        final double EARTH_RADIUS_METERS = 6371000.0;
+
+        double dLat = Math.toRadians(lat2 - lat1);
+        double dLon = Math.toRadians(lon2 - lon1);
+
+        double a = Math.sin(dLat / 2) * Math.sin(dLat / 2)
+                + Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2))
+                * Math.sin(dLon / 2) * Math.sin(dLon / 2);
+
+        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+
+        return EARTH_RADIUS_METERS * c;
+    }
+
+    /**
+     * Get a randomized display center for a privacy zone.
+     * The randomization is consistent per activity (seeded by activity ID).
+     * Offset is within 10-15% of the radius from the true center.
+     *
+     * @param zone the privacy zone
+     * @param activityId the activity ID (for consistent seeding)
+     * @return randomized Point for display
+     */
+    public Point getRandomizedDisplayCenter(PrivacyZone zone, UUID activityId) {
+        Point trueCenter = zone.getCenterPoint();
+        int radiusMeters = zone.getRadiusMeters();
+
+        // Seed Random with activity ID for consistency
+        Random random = new Random(activityId.getMostSignificantBits() ^ activityId.getLeastSignificantBits());
+
+        // Random offset within 10-15% of radius
+        double offsetPercent = 0.10 + random.nextDouble() * 0.05; // 10-15%
+        double offsetMeters = radiusMeters * offsetPercent;
+
+        // Random angle in radians
+        double angle = random.nextDouble() * 2 * Math.PI;
+
+        // Convert offset to degrees (approximate)
+        double degreesPerMeter = 1.0 / 111320.0; // At equator
+        double offsetDegrees = offsetMeters * degreesPerMeter;
+
+        // Calculate randomized coordinates
+        double randomLat = trueCenter.getY() + (offsetDegrees * Math.sin(angle));
+        double randomLon = trueCenter.getX() + (offsetDegrees * Math.cos(angle) / Math.cos(Math.toRadians(trueCenter.getY())));
+
+        return geometryFactory.createPoint(new Coordinate(randomLon, randomLat));
+    }
+
+    /**
+     * Get randomized display center as lat/lon coordinates.
+     *
+     * @param zone the privacy zone
+     * @param activityId the activity ID (for consistent seeding)
+     * @return array [latitude, longitude]
+     */
+    public double[] getRandomizedDisplayCenterCoordinates(PrivacyZone zone, UUID activityId) {
+        Point randomized = getRandomizedDisplayCenter(zone, activityId);
+        return new double[]{randomized.getY(), randomized.getX()};
+    }
+}
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index 4f3e5b8..bf5d4f3 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -44,6 +44,15 @@ spring:
       write-dates-as-timestamps: false
     time-zone: UTC
 
+  # Cache configuration for privacy zone filtering
+  cache:
+    type: caffeine
+    cache-names:
+      - filteredTracks
+      - filteredTrackPoints
+    caffeine:
+      spec: maximumSize=1000,expireAfterWrite=7d
+
 # FitPub specific configuration
 fitpub:
   # Domain and URL configuration
diff --git a/src/main/resources/db/migration/V18__create_privacy_zones_table.sql b/src/main/resources/db/migration/V18__create_privacy_zones_table.sql
new file mode 100644
index 0000000..2e767bf
--- /dev/null
+++ b/src/main/resources/db/migration/V18__create_privacy_zones_table.sql
@@ -0,0 +1,37 @@
+CREATE EXTENSION btree_gist;
+
+-- Privacy Zones Table
+-- Stores user-defined geographic zones where GPS data should be filtered
+CREATE TABLE privacy_zones (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    name VARCHAR(100) NOT NULL,
+    description TEXT,
+
+    -- Center point of the privacy zone (PostGIS Point geometry)
+    center_point geometry(Point, 4326) NOT NULL,
+
+    -- Radius in meters
+    radius_meters INTEGER NOT NULL,
+
+    -- Whether this zone is active (allows temporary disabling)
+    is_active BOOLEAN NOT NULL DEFAULT TRUE,
+
+    -- Timestamps
+    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMP NOT NULL DEFAULT NOW(),
+
+    -- Constraints
+    CONSTRAINT chk_radius_positive CHECK (radius_meters > 0 AND radius_meters <= 10000)
+);
+
+-- Indexes for efficient spatial queries
+CREATE INDEX idx_privacy_zones_user ON privacy_zones(user_id) WHERE is_active = TRUE;
+CREATE INDEX idx_privacy_zones_center_point ON privacy_zones USING GIST(center_point);
+
+-- Composite spatial index for user + geometry queries
+CREATE INDEX idx_privacy_zones_user_spatial ON privacy_zones USING GIST(user_id, center_point) WHERE is_active = TRUE;
+
+COMMENT ON TABLE privacy_zones IS 'User-defined geographic zones for GPS track privacy filtering';
+COMMENT ON COLUMN privacy_zones.center_point IS 'True center of privacy zone (not the randomized display center)';
+COMMENT ON COLUMN privacy_zones.radius_meters IS 'Radius of privacy zone in meters (max 10km for safety)';
diff --git a/src/main/resources/static/js/privacy-zones.js b/src/main/resources/static/js/privacy-zones.js
new file mode 100644
index 0000000..d082fc3
--- /dev/null
+++ b/src/main/resources/static/js/privacy-zones.js
@@ -0,0 +1,390 @@
+/**
+ * Privacy Zones Management Module
+ * Handles GPS privacy zone creation, editing, and deletion with interactive Leaflet map.
+ */
+const PrivacyZones = (() => {
+    let map = null;
+    let marker = null;
+    let circle = null;
+    let zones = [];
+    let currentZone = null;
+
+    /**
+     * Initialize the privacy zones module
+     */
+    function init() {
+        setupEventListeners();
+        loadZones();
+    }
+
+    /**
+     * Setup event listeners for UI interactions
+     */
+    function setupEventListeners() {
+        const startAddZoneBtn = document.getElementById('startAddZoneBtn');
+        const cancelZoneBtn = document.getElementById('cancelZoneBtn');
+        const zoneDetailsForm = document.getElementById('zoneDetailsForm');
+        const zoneRadiusInput = document.getElementById('zoneRadius');
+        const radiusValue = document.getElementById('radiusValue');
+
+        startAddZoneBtn.addEventListener('click', startAddingZone);
+        cancelZoneBtn.addEventListener('click', cancelZone);
+        zoneDetailsForm.addEventListener('submit', saveZone);
+
+        // Update radius display and circle in real-time
+        zoneRadiusInput.addEventListener('input', (e) => {
+            const radius = parseInt(e.target.value);
+            radiusValue.textContent = radius;
+            if (circle) {
+                circle.setRadius(radius);
+            }
+        });
+    }
+
+    /**
+     * Start the process of adding a new zone
+     */
+    function startAddingZone() {
+        const formContainer = document.getElementById('addZoneForm');
+        formContainer.classList.remove('d-none');
+
+        // Initialize map if not already done
+        if (!map) {
+            initMap();
+        }
+
+        // Reset form
+        document.getElementById('zoneId').value = '';
+        document.getElementById('zoneName').value = '';
+        document.getElementById('zoneDescription').value = '';
+        document.getElementById('zoneLatitude').value = '';
+        document.getElementById('zoneLongitude').value = '';
+        document.getElementById('zoneRadius').value = 200;
+        document.getElementById('radiusValue').textContent = '200';
+
+        // Clear existing marker and circle
+        if (marker) {
+            map.removeLayer(marker);
+            marker = null;
+        }
+        if (circle) {
+            map.removeLayer(circle);
+            circle = null;
+        }
+
+        currentZone = null;
+    }
+
+    /**
+     * Cancel zone creation/editing
+     */
+    function cancelZone() {
+        const formContainer = document.getElementById('addZoneForm');
+        formContainer.classList.add('d-none');
+
+        if (marker) {
+            map.removeLayer(marker);
+            marker = null;
+        }
+        if (circle) {
+            map.removeLayer(circle);
+            circle = null;
+        }
+
+        currentZone = null;
+    }
+
+    /**
+     * Initialize the Leaflet map
+     */
+    function initMap() {
+        const mapContainer = document.getElementById('zoneMap');
+
+        // Initialize map centered on user's location (or default)
+        map = L.map(mapContainer).setView([51.505, -0.09], 13);
+
+        // Add OpenStreetMap tiles
+        L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
+            attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
+            maxZoom: 19
+        }).addTo(map);
+
+        // Try to get user's current location
+        if (navigator.geolocation) {
+            navigator.geolocation.getCurrentPosition(
+                (position) => {
+                    const lat = position.coords.latitude;
+                    const lon = position.coords.longitude;
+                    map.setView([lat, lon], 15);
+                },
+                (error) => {
+                    console.warn('Geolocation error:', error);
+                }
+            );
+        }
+
+        // Handle map clicks to place marker
+        map.on('click', (e) => {
+            placeMarker(e.latlng.lat, e.latlng.lng);
+        });
+    }
+
+    /**
+     * Place a marker and circle on the map
+     */
+    function placeMarker(lat, lon) {
+        const radius = parseInt(document.getElementById('zoneRadius').value);
+
+        // Remove existing marker and circle
+        if (marker) {
+            map.removeLayer(marker);
+        }
+        if (circle) {
+            map.removeLayer(circle);
+        }
+
+        // Create new marker
+        marker = L.marker([lat, lon], {
+            draggable: true
+        }).addTo(map);
+
+        // Create circle
+        circle = L.circle([lat, lon], {
+            color: '#dc3545',
+            fillColor: '#dc3545',
+            fillOpacity: 0.2,
+            radius: radius
+        }).addTo(map);
+
+        // Update form fields
+        document.getElementById('zoneLatitude').value = lat.toFixed(6);
+        document.getElementById('zoneLongitude').value = lon.toFixed(6);
+
+        // Handle marker dragging
+        marker.on('drag', (e) => {
+            const position = e.target.getLatLng();
+            circle.setLatLng(position);
+            document.getElementById('zoneLatitude').value = position.lat.toFixed(6);
+            document.getElementById('zoneLongitude').value = position.lng.toFixed(6);
+        });
+    }
+
+    /**
+     * Save a privacy zone (create or update)
+     */
+    async function saveZone(e) {
+        e.preventDefault();
+
+        const zoneId = document.getElementById('zoneId').value;
+        const name = document.getElementById('zoneName').value.trim();
+        const description = document.getElementById('zoneDescription').value.trim();
+        const latitude = parseFloat(document.getElementById('zoneLatitude').value);
+        const longitude = parseFloat(document.getElementById('zoneLongitude').value);
+        const radiusMeters = parseInt(document.getElementById('zoneRadius').value);
+
+        if (!latitude || !longitude) {
+            FitPub.showAlert('Please click on the map to place a privacy zone', 'warning');
+            return;
+        }
+
+        const saveBtn = document.getElementById('saveZoneBtn');
+        saveBtn.disabled = true;
+        saveBtn.innerHTML = '<span class="spinner-border spinner-border-sm"></span> Saving...';
+
+        try {
+            const url = zoneId ? `/api/privacy-zones/${zoneId}` : '/api/privacy-zones';
+            const method = zoneId ? 'PUT' : 'POST';
+
+            const response = await FitPubAuth.authenticatedFetch(url, {
+                method: method,
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    name,
+                    description,
+                    latitude,
+                    longitude,
+                    radiusMeters
+                })
+            });
+
+            if (response.ok) {
+                FitPub.showAlert(zoneId ? 'Privacy zone updated' : 'Privacy zone created', 'success');
+                cancelZone();
+                loadZones();
+            } else {
+                const error = await response.json();
+                FitPub.showAlert(error.message || 'Failed to save privacy zone', 'danger');
+            }
+        } catch (error) {
+            console.error('Save zone error:', error);
+            FitPub.showAlert('Network error. Please try again.', 'danger');
+        } finally {
+            saveBtn.disabled = false;
+            saveBtn.innerHTML = '<i class="bi bi-check-circle"></i> Save Zone';
+        }
+    }
+
+    /**
+     * Load all privacy zones from the API
+     */
+    async function loadZones() {
+        const loadingEl = document.getElementById('zonesListLoading');
+        const emptyEl = document.getElementById('zonesListEmpty');
+        const listEl = document.getElementById('zonesList');
+
+        loadingEl.classList.remove('d-none');
+        emptyEl.classList.add('d-none');
+        listEl.innerHTML = '';
+
+        try {
+            const response = await FitPubAuth.authenticatedFetch('/api/privacy-zones');
+
+            if (response.ok) {
+                zones = await response.json();
+                loadingEl.classList.add('d-none');
+
+                if (zones.length === 0) {
+                    emptyEl.classList.remove('d-none');
+                } else {
+                    renderZonesList();
+                }
+            } else {
+                loadingEl.classList.add('d-none');
+                FitPub.showAlert('Failed to load privacy zones', 'danger');
+            }
+        } catch (error) {
+            console.error('Load zones error:', error);
+            loadingEl.classList.add('d-none');
+            FitPub.showAlert('Network error. Please try again.', 'danger');
+        }
+    }
+
+    /**
+     * Render the list of privacy zones
+     */
+    function renderZonesList() {
+        const listEl = document.getElementById('zonesList');
+        listEl.innerHTML = '';
+
+        zones.forEach(zone => {
+            const item = document.createElement('div');
+            item.className = 'list-group-item';
+            item.innerHTML = `
+                <div class="d-flex justify-content-between align-items-start">
+                    <div class="flex-grow-1">
+                        <h6 class="mb-1">
+                            ${escapeHtml(zone.name)}
+                            ${zone.isActive ? '<span class="badge bg-success ms-2">Active</span>' : '<span class="badge bg-secondary ms-2">Inactive</span>'}
+                        </h6>
+                        ${zone.description ? `<p class="mb-1 small text-muted">${escapeHtml(zone.description)}</p>` : ''}
+                        <p class="mb-0 small text-muted">
+                            <i class="bi bi-geo-alt"></i> ${zone.latitude.toFixed(6)}, ${zone.longitude.toFixed(6)} &middot;
+                            <i class="bi bi-circle"></i> ${zone.radiusMeters}m radius
+                        </p>
+                    </div>
+                    <div class="btn-group btn-group-sm" role="group">
+                        <button class="btn btn-outline-secondary" onclick="PrivacyZones.editZone('${zone.id}')" title="Edit">
+                            <i class="bi bi-pencil"></i>
+                        </button>
+                        <button class="btn btn-outline-${zone.isActive ? 'warning' : 'success'}" onclick="PrivacyZones.toggleZone('${zone.id}', ${!zone.isActive})" title="${zone.isActive ? 'Deactivate' : 'Activate'}">
+                            <i class="bi bi-${zone.isActive ? 'pause' : 'play'}"></i>
+                        </button>
+                        <button class="btn btn-outline-danger" onclick="PrivacyZones.deleteZone('${zone.id}')" title="Delete">
+                            <i class="bi bi-trash"></i>
+                        </button>
+                    </div>
+                </div>
+            `;
+            listEl.appendChild(item);
+        });
+    }
+
+    /**
+     * Edit a privacy zone
+     */
+    function editZone(zoneId) {
+        const zone = zones.find(z => z.id === zoneId);
+        if (!zone) return;
+
+        startAddingZone();
+
+        // Populate form
+        document.getElementById('zoneId').value = zone.id;
+        document.getElementById('zoneName').value = zone.name;
+        document.getElementById('zoneDescription').value = zone.description || '';
+        document.getElementById('zoneRadius').value = zone.radiusMeters;
+        document.getElementById('radiusValue').textContent = zone.radiusMeters;
+
+        // Place marker on map
+        placeMarker(zone.latitude, zone.longitude);
+        map.setView([zone.latitude, zone.longitude], 15);
+
+        currentZone = zone;
+    }
+
+    /**
+     * Toggle a zone's active status
+     */
+    async function toggleZone(zoneId, isActive) {
+        try {
+            const response = await FitPubAuth.authenticatedFetch(`/api/privacy-zones/${zoneId}/toggle`, {
+                method: 'PATCH',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ isActive })
+            });
+
+            if (response.ok) {
+                FitPub.showAlert(`Privacy zone ${isActive ? 'activated' : 'deactivated'}`, 'success');
+                loadZones();
+            } else {
+                FitPub.showAlert('Failed to toggle privacy zone', 'danger');
+            }
+        } catch (error) {
+            console.error('Toggle zone error:', error);
+            FitPub.showAlert('Network error. Please try again.', 'danger');
+        }
+    }
+
+    /**
+     * Delete a privacy zone
+     */
+    async function deleteZone(zoneId) {
+        if (!confirm('Are you sure you want to delete this privacy zone? This will immediately affect all existing activities.')) {
+            return;
+        }
+
+        try {
+            const response = await FitPubAuth.authenticatedFetch(`/api/privacy-zones/${zoneId}`, {
+                method: 'DELETE'
+            });
+
+            if (response.ok) {
+                FitPub.showAlert('Privacy zone deleted', 'success');
+                loadZones();
+            } else {
+                FitPub.showAlert('Failed to delete privacy zone', 'danger');
+            }
+        } catch (error) {
+            console.error('Delete zone error:', error);
+            FitPub.showAlert('Network error. Please try again.', 'danger');
+        }
+    }
+
+    /**
+     * Escape HTML to prevent XSS
+     */
+    function escapeHtml(text) {
+        if (!text) return '';
+        const div = document.createElement('div');
+        div.textContent = text;
+        return div.innerHTML;
+    }
+
+    // Public API
+    return {
+        init,
+        editZone,
+        toggleZone,
+        deleteZone
+    };
+})();
diff --git a/src/main/resources/templates/activities/detail.html b/src/main/resources/templates/activities/detail.html
index 816e03a..1344d35 100644
--- a/src/main/resources/templates/activities/detail.html
+++ b/src/main/resources/templates/activities/detail.html
@@ -569,7 +569,7 @@
                     if (hasGpsTrack && activity.simplifiedTrack) {
                         document.getElementById('mapSection').style.display = 'block';
                         document.getElementById('indoorPlaceholder').style.display = 'none';
-                        renderMap(activity.simplifiedTrack);
+                        renderMap(activity.simplifiedTrack, activity);
                     } else {
                         // Show indoor activity placeholder
                         document.getElementById('mapSection').style.display = 'none';
@@ -710,7 +710,7 @@
                     }
                 }
 
-                function renderMap(simplifiedTrack) {
+                function renderMap(simplifiedTrack, activity) {
                     // Parse GeoJSON from simplifiedTrack
                     const geoJson = {
                         type: 'LineString',
@@ -765,6 +765,15 @@
                             }
                         }
 
+                        // Render privacy zones if present (owner view only)
+                        console.log('Privacy zones in response:', activity.privacyZones);
+                        if (activity.privacyZones && activity.privacyZones.length > 0) {
+                            console.log('Rendering', activity.privacyZones.length, 'privacy zones');
+                            renderPrivacyZones(activityMap, activity.privacyZones);
+                        } else {
+                            console.log('No privacy zones to render');
+                        }
+
                         // Force fit bounds again after map is fully rendered
                         if (activityMap && activityMap.trackLayer) {
                             setTimeout(() => {
@@ -781,6 +790,60 @@
                     }, 50);
                 }
 
+                function renderPrivacyZones(map, zones) {
+                    // Helper to escape HTML
+                    const escapeHtml = (text) => {
+                        const div = document.createElement('div');
+                        div.textContent = text;
+                        return div.innerHTML;
+                    };
+
+                    // Render each privacy zone as a translucent red circle
+                    zones.forEach(zone => {
+                        const circle = L.circle([zone.latitude, zone.longitude], {
+                            color: '#dc3545',
+                            fillColor: '#dc3545',
+                            fillOpacity: 0.1,
+                            opacity: 0.4,
+                            weight: 2,
+                            dashArray: '5, 10',
+                            radius: zone.radiusMeters
+                        }).addTo(map);
+
+                        // Add tooltip
+                        const zoneName = escapeHtml(zone.name || 'Privacy Zone');
+                        circle.bindTooltip(
+                            `<strong>🔒 Privacy Zone</strong><br>${zoneName}<br><small class="text-muted">Hidden for others</small>`,
+                            {
+                                permanent: false,
+                                direction: 'top',
+                                className: 'privacy-zone-tooltip'
+                            }
+                        );
+                    });
+
+                    // Add CSS for privacy zone tooltip
+                    if (!document.getElementById('privacy-zone-tooltip-style')) {
+                        const style = document.createElement('style');
+                        style.id = 'privacy-zone-tooltip-style';
+                        style.textContent = `
+                            .privacy-zone-tooltip {
+                                background: rgba(220, 53, 69, 0.95);
+                                color: white;
+                                border: none;
+                                border-radius: 4px;
+                                padding: 8px 12px;
+                                font-size: 13px;
+                                box-shadow: 0 2px 8px rgba(0,0,0,0.3);
+                            }
+                            .privacy-zone-tooltip::before {
+                                border-top-color: rgba(220, 53, 69, 0.95);
+                            }
+                        `;
+                        document.head.appendChild(style);
+                    }
+                }
+
                 function renderElevationChart(trackPoints) {
                     // Calculate cumulative distance and prepare elevation data
                     let cumulativeDistance = 0;
diff --git a/src/main/resources/templates/settings.html b/src/main/resources/templates/settings.html
index 07046f5..6bef17a 100644
--- a/src/main/resources/templates/settings.html
+++ b/src/main/resources/templates/settings.html
@@ -32,15 +32,15 @@
                                 <p class="mb-1">Update your display name, bio, and avatar</p>
                             </a>
 
-                            <div class="list-group-item list-group-item-action disabled">
+                            <a href="#privacyZones" class="list-group-item list-group-item-action" id="privacyZonesLink">
                                 <div class="d-flex w-100 justify-content-between">
                                     <h5 class="mb-1">
-                                        <i class="bi bi-shield-lock"></i> Privacy Settings
+                                        <i class="bi bi-shield-lock"></i> Privacy Zones
                                     </h5>
-                                    <small class="text-muted">Coming soon</small>
+                                    <small><i class="bi bi-chevron-right"></i></small>
                                 </div>
-                                <p class="mb-1 text-muted">Manage your privacy and data preferences</p>
-                            </div>
+                                <p class="mb-1">Define private GPS zones to protect your home and other sensitive locations</p>
+                            </a>
 
                             <div class="list-group-item list-group-item-action disabled">
                                 <div class="d-flex w-100 justify-content-between">
@@ -73,8 +73,104 @@
                             </div>
                         </div>
 
+                        <!-- Privacy Zones Section (hidden by default) -->
+                        <div id="privacyZonesSection" class="d-none mt-4">
+                            <div class="d-flex align-items-center mb-3">
+                                <button class="btn btn-sm btn-outline-secondary me-3" id="backToSettings">
+                                    <i class="bi bi-arrow-left"></i> Back
+                                </button>
+                                <h5 class="mb-0">
+                                    <i class="bi bi-shield-lock"></i> GPS Privacy Zones
+                                </h5>
+                            </div>
+
+                            <div class="alert alert-info">
+                                <i class="bi bi-info-circle"></i>
+                                <strong>Privacy Protection:</strong> GPS coordinates within your privacy zones will be automatically removed from all public activity maps and Fediverse share images. Changes apply retroactively to all existing activities.
+                            </div>
+
+                            <!-- Add Zone Form -->
+                            <div class="card mb-4">
+                                <div class="card-header d-flex justify-content-between align-items-center">
+                                    <h6 class="mb-0">Add Privacy Zone</h6>
+                                    <button class="btn btn-sm btn-primary" id="startAddZoneBtn">
+                                        <i class="bi bi-plus-circle"></i> Add Zone
+                                    </button>
+                                </div>
+                                <div class="card-body d-none" id="addZoneForm">
+                                    <div class="row">
+                                        <div class="col-md-6">
+                                            <!-- Map for zone placement -->
+                                            <div id="zoneMap" style="height: 400px; width: 100%;"></div>
+                                            <small class="text-muted">Click on the map to place a privacy zone</small>
+                                        </div>
+                                        <div class="col-md-6">
+                                            <form id="zoneDetailsForm">
+                                                <input type="hidden" id="zoneId">
+                                                <div class="mb-3">
+                                                    <label for="zoneName" class="form-label">Name *</label>
+                                                    <input type="text" class="form-control" id="zoneName" required maxlength="100" placeholder="e.g., Home, Office">
+                                                </div>
+                                                <div class="mb-3">
+                                                    <label for="zoneDescription" class="form-label">Description</label>
+                                                    <textarea class="form-control" id="zoneDescription" rows="2" maxlength="500" placeholder="Optional description"></textarea>
+                                                </div>
+                                                <div class="row">
+                                                    <div class="col-md-6 mb-3">
+                                                        <label for="zoneLatitude" class="form-label">Latitude *</label>
+                                                        <input type="number" class="form-control" id="zoneLatitude" step="0.000001" readonly required>
+                                                    </div>
+                                                    <div class="col-md-6 mb-3">
+                                                        <label for="zoneLongitude" class="form-label">Longitude *</label>
+                                                        <input type="number" class="form-control" id="zoneLongitude" step="0.000001" readonly required>
+                                                    </div>
+                                                </div>
+                                                <div class="mb-3">
+                                                    <label for="zoneRadius" class="form-label">Radius (meters) *</label>
+                                                    <input type="range" class="form-range" id="zoneRadius" min="50" max="10000" value="200" step="50">
+                                                    <div class="d-flex justify-content-between">
+                                                        <small class="text-muted">50m</small>
+                                                        <small><strong id="radiusValue">200</strong> meters</small>
+                                                        <small class="text-muted">10km</small>
+                                                    </div>
+                                                </div>
+                                                <div class="d-flex gap-2">
+                                                    <button type="submit" class="btn btn-primary flex-grow-1" id="saveZoneBtn">
+                                                        <i class="bi bi-check-circle"></i> Save Zone
+                                                    </button>
+                                                    <button type="button" class="btn btn-secondary" id="cancelZoneBtn">
+                                                        <i class="bi bi-x-circle"></i> Cancel
+                                                    </button>
+                                                </div>
+                                            </form>
+                                        </div>
+                                    </div>
+                                </div>
+                            </div>
+
+                            <!-- Existing Zones List -->
+                            <div class="card">
+                                <div class="card-header">
+                                    <h6 class="mb-0">Your Privacy Zones</h6>
+                                </div>
+                                <div class="card-body">
+                                    <div id="zonesListLoading" class="text-center py-4">
+                                        <div class="spinner-border text-primary" role="status">
+                                            <span class="visually-hidden">Loading zones...</span>
+                                        </div>
+                                    </div>
+                                    <div id="zonesListEmpty" class="text-center py-4 text-muted d-none">
+                                        <i class="bi bi-shield-lock" style="font-size: 3rem;"></i>
+                                        <p class="mt-3">No privacy zones defined yet.</p>
+                                        <p class="small">Click "Add Zone" above to create your first privacy zone.</p>
+                                    </div>
+                                    <div id="zonesList" class="list-group list-group-flush"></div>
+                                </div>
+                            </div>
+                        </div>
+
                         <!-- Danger Zone: Delete Account -->
-                        <div class="mt-5">
+                        <div class="mt-5" id="dangerZone">
                             <h5 class="text-danger">
                                 <i class="bi bi-exclamation-triangle-fill"></i> Danger Zone
                             </h5>
@@ -153,6 +249,7 @@
 
     <!-- Custom Scripts -->
     <th:block layout:fragment="scripts">
+        <script src="/js/privacy-zones.js"></script>
         <script>
             document.addEventListener('DOMContentLoaded', function() {
                 // Redirect to login if not authenticated
@@ -161,6 +258,31 @@
                     return;
                 }
 
+                // Privacy Zones navigation
+                const settingsContent = document.querySelector('.list-group');
+                const privacyZonesSection = document.getElementById('privacyZonesSection');
+                const dangerZone = document.getElementById('dangerZone');
+                const privacyZonesLink = document.getElementById('privacyZonesLink');
+                const backToSettings = document.getElementById('backToSettings');
+
+                privacyZonesLink.addEventListener('click', (e) => {
+                    e.preventDefault();
+                    settingsContent.classList.add('d-none');
+                    dangerZone.classList.add('d-none');
+                    privacyZonesSection.classList.remove('d-none');
+
+                    // Initialize privacy zones module
+                    if (typeof PrivacyZones !== 'undefined') {
+                        PrivacyZones.init();
+                    }
+                });
+
+                backToSettings.addEventListener('click', () => {
+                    privacyZonesSection.classList.add('d-none');
+                    settingsContent.classList.remove('d-none');
+                    dangerZone.classList.remove('d-none');
+                });
+
                 const modal = new bootstrap.Modal(document.getElementById('deleteAccountModal'));
                 const deletePasswordInput = document.getElementById('deletePasswordInput');
                 const confirmDeleteBtn = document.getElementById('confirmDeleteBtn');