diff --git a/src/common/config.rs b/src/common/config.rs
index 428ef70c..3b7d1883 100644
--- a/src/common/config.rs
+++ b/src/common/config.rs
@@ -618,6 +618,9 @@ pub struct FeaturesConfig {
     pub enable_trash: bool,
     pub enable_search: bool,
     pub enable_music: bool,
+    /// Expose other OxiCloud users as a read-only "system" address book
+    /// at GET /api/address-books. Set to false to hide the user directory.
+    pub expose_system_users: bool,
 }
 
 impl Default for FeaturesConfig {
@@ -629,6 +632,7 @@ impl Default for FeaturesConfig {
             enable_trash: true,        // Enable trash feature
             enable_search: true,       // Enable search feature
             enable_music: true,        // Enable music feature
+            expose_system_users: true, // Expose OxiCloud users as address book by default
         }
     }
 }
@@ -948,6 +952,12 @@ impl AppConfig {
             config.features.enable_music = val;
         }
 
+        if let Ok(v) = env::var("OXICLOUD_EXPOSE_SYSTEM_USERS").map(|v| v.parse::<bool>())
+            && let Ok(val) = v
+        {
+            config.features.expose_system_users = val;
+        }
+
         // Storage limits
         if let Ok(max_upload) = env::var("OXICLOUD_MAX_UPLOAD_SIZE").map(|v| v.parse::<usize>())
             && let Ok(val) = max_upload
diff --git a/src/interfaces/api/handlers/contacts_handler.rs b/src/interfaces/api/handlers/contacts_handler.rs
index 13ce917e..99604da7 100644
--- a/src/interfaces/api/handlers/contacts_handler.rs
+++ b/src/interfaces/api/handlers/contacts_handler.rs
@@ -30,6 +30,8 @@ const SYSTEM_BOOK_ID: &str = "system";
 pub struct ContactsApiState {
     pub contact_service: Arc<ContactStorageAdapter>,
     pub auth_service: Option<Arc<AuthApplicationService>>,
+    /// When false, the virtual "system" address book (OxiCloud users) is hidden.
+    pub expose_system_users: bool,
 }
 
 /// Address book entry with `is_readonly` and `is_system` flags.
@@ -251,7 +253,7 @@ pub async fn list_address_books(
                 })
                 .collect();
 
-            if state.auth_service.is_some() {
+            if state.expose_system_users && state.auth_service.is_some() {
                 let now = Utc::now();
                 response.push(AddressBookResponse {
                     id: SYSTEM_BOOK_ID.to_string(),
@@ -438,6 +440,9 @@ pub async fn list_contacts(
     Query(params): Query<ListQuery>,
 ) -> impl IntoResponse {
     if book_id == SYSTEM_BOOK_ID {
+        if !state.expose_system_users {
+            return system_book_unavailable();
+        }
         let Some(auth_service) = &state.auth_service else {
             return system_book_unavailable();
         };
@@ -544,6 +549,9 @@ pub async fn get_contact(
     Path((book_id, contact_id)): Path<(String, String)>,
 ) -> impl IntoResponse {
     if book_id == SYSTEM_BOOK_ID {
+        if !state.expose_system_users {
+            return system_book_unavailable();
+        }
         let Some(auth_service) = &state.auth_service else {
             return system_book_unavailable();
         };
diff --git a/src/interfaces/api/routes.rs b/src/interfaces/api/routes.rs
index 0c2e8b57..b070bf88 100644
--- a/src/interfaces/api/routes.rs
+++ b/src/interfaces/api/routes.rs
@@ -405,6 +405,7 @@ pub fn create_api_routes(app_state: &Arc<AppState>) -> Router<Arc<AppState>> {
         let contacts_state = ContactsApiState {
             contact_service,
             auth_service: auth_svc,
+            expose_system_users: app_state.core.config.features.expose_system_users,
         };
 
         let contacts_router = Router::new()