diff --git a/README.md b/README.md
index e907cfc..aad9f24 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
 
 Flutter mobile frontend for the private Metatron-Drive file workspace.
 
+The app uses one global account with multiple organization memberships. New accounts apply with an organization code; organization administrators must approve access before login.
+
 ## Run
 
 ```bash
diff --git a/lib/controllers/session_controller.dart b/lib/controllers/session_controller.dart
index 416efef..c100dc8 100644
--- a/lib/controllers/session_controller.dart
+++ b/lib/controllers/session_controller.dart
@@ -11,6 +11,14 @@ class SessionController extends ChangeNotifier {
   final TokenStore tokens;
   SessionStatus status = SessionStatus.loading;
   UserProfile? user;
+  String? organizationId;
+
+  OrganizationMembership? get membership {
+    final matches = user?.approvedMemberships.where(
+      (item) => item.organization.id == organizationId,
+    );
+    return matches == null || matches.isEmpty ? null : matches.first;
+  }
 
   Future<void> initialize() async {
     final minimumSplash = Future<void>.delayed(
@@ -22,6 +30,10 @@ class SessionController extends ChangeNotifier {
     } else {
       try {
         user = await api.me();
+        await _selectInitialOrganization();
+        if (organizationId == null) {
+          throw StateError('No approved organization membership');
+        }
         status = SessionStatus.signedIn;
       } catch (_) {
         await tokens.clear();
@@ -36,21 +48,46 @@ class SessionController extends ChangeNotifier {
     final result = await api.login(username, password);
     await tokens.write(result.token);
     user = result.user;
+    await _selectInitialOrganization();
     status = SessionStatus.signedIn;
     notifyListeners();
   }
 
-  Future<void> register(Map<String, dynamic> input) async {
-    final result = await api.register(input);
-    await tokens.write(result.token);
-    user = result.user;
-    status = SessionStatus.signedIn;
+  Future<String> register(Map<String, dynamic> input) => api.register(input);
+
+  Future<void> _selectInitialOrganization() async {
+    final approved = user?.approvedMemberships ?? const [];
+    final saved = await tokens.readOrganization();
+    final selected = approved.where((item) => item.organization.id == saved);
+    organizationId = selected.isNotEmpty
+        ? selected.first.organization.id
+        : (approved.isEmpty ? null : approved.first.organization.id);
+    if (organizationId != null) {
+      await tokens.writeOrganization(organizationId!);
+    }
+  }
+
+  Future<void> selectOrganization(String id) async {
+    if (!(user?.approvedMemberships.any((item) => item.organization.id == id) ??
+        false)) {
+      return;
+    }
+    organizationId = id;
+    await tokens.writeOrganization(id);
+    notifyListeners();
+  }
+
+  Future<void> refreshProfile() async {
+    user = await api.me();
+    await _selectInitialOrganization();
     notifyListeners();
   }
 
   Future<void> logout() async {
     await tokens.clear();
+    await tokens.clearOrganization();
     user = null;
+    organizationId = null;
     status = SessionStatus.signedOut;
     notifyListeners();
   }
diff --git a/lib/controllers/upload_controller.dart b/lib/controllers/upload_controller.dart
index 87d46e1..b043c28 100644
--- a/lib/controllers/upload_controller.dart
+++ b/lib/controllers/upload_controller.dart
@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:background_downloader/background_downloader.dart';
@@ -17,6 +18,7 @@ class UploadRecord {
     this.status = TaskStatus.enqueued,
     this.sizeBytes = -1,
     this.errorMessage,
+    this.organizationId,
   });
 
   final String taskId;
@@ -27,6 +29,7 @@ class UploadRecord {
   final TaskStatus status;
   final int sizeBytes;
   final String? errorMessage;
+  final String? organizationId;
 
   bool get isFinished => status.isFinalState;
   bool get canRetry => status == TaskStatus.failed;
@@ -45,6 +48,7 @@ class UploadRecord {
     status: status ?? this.status,
     sizeBytes: sizeBytes ?? this.sizeBytes,
     errorMessage: errorMessage ?? this.errorMessage,
+    organizationId: organizationId,
   );
 }
 
@@ -64,15 +68,28 @@ class UploadController extends ChangeNotifier {
   final Map<String, Task> _tasks = {};
   bool _notificationPermissionChecked = false;
   bool _disposed = false;
+  String? _organizationId;
 
   List<UploadRecord> get uploads {
-    final result = _uploads.values.toList()
-      ..sort((a, b) => b.createdAt.compareTo(a.createdAt));
+    final result =
+        _uploads.values
+            .where(
+              (item) =>
+                  item.organizationId == null ||
+                  item.organizationId == _organizationId,
+            )
+            .toList()
+          ..sort((a, b) => b.createdAt.compareTo(a.createdAt));
     return result;
   }
 
   int completedVersion = 0;
 
+  void selectOrganization(String? organizationId) {
+    if (_organizationId == organizationId) return;
+    _organizationId = organizationId;
+  }
+
   Future<void> _restoreHistory() async {
     // start() initializes tracking asynchronously during application startup.
     // A short retry also covers slower devices on their first launch.
@@ -102,6 +119,8 @@ class UploadController extends ChangeNotifier {
     await _ensureNotificationPermission();
     final token = await _tokens.read();
     if (token == null) throw StateError('Your session has expired');
+    final organizationId = await _tokens.readOrganization();
+    if (organizationId == null) throw StateError('Select an organization');
     final task = UploadTask(
       url: '${AppConfig.apiBaseUrl}/files/upload',
       filename: filename,
@@ -109,12 +128,18 @@ class UploadController extends ChangeNotifier {
       baseDirectory: BaseDirectory.applicationSupport,
       fileField: 'file',
       fields: folderId == null ? const {} : {'folderId': folderId},
-      headers: {'Authorization': 'Bearer $token'},
+      headers: {
+        'Authorization': 'Bearer $token',
+        'X-Organization-Id': organizationId,
+      },
       group: 'uploads',
       updates: Updates.statusAndProgress,
       retries: 2,
       displayName: displayName,
-      metaData: displayName,
+      metaData: jsonEncode({
+        'name': displayName,
+        'organizationId': organizationId,
+      }),
     );
     _tasks[task.taskId] = task;
     _uploads[task.taskId] = UploadRecord(
@@ -122,6 +147,7 @@ class UploadController extends ChangeNotifier {
       name: displayName,
       filename: filename,
       createdAt: task.creationTime,
+      organizationId: organizationId,
     );
     notifyListeners();
     final accepted = await FileDownloader().enqueue(task);
@@ -180,23 +206,40 @@ class UploadController extends ChangeNotifier {
     _tasks[record.taskId] = record.task;
     _uploads[record.taskId] = UploadRecord(
       taskId: record.taskId,
-      name: record.task.displayName,
+      name: _taskName(record.task),
       filename: record.task.filename,
       createdAt: record.task.creationTime,
       progress: record.progress.clamp(0, 1),
       status: record.status,
       sizeBytes: record.expectedFileSize,
       errorMessage: record.exception?.description,
+      organizationId: _taskOrganization(record.task),
     );
   }
 
   UploadRecord _fromTask(Task task) => UploadRecord(
     taskId: task.taskId,
-    name: task.displayName,
+    name: _taskName(task),
     filename: task.filename,
     createdAt: task.creationTime,
+    organizationId: _taskOrganization(task),
   );
 
+  Map<String, dynamic>? _taskMetadata(Task task) {
+    try {
+      final value = jsonDecode(task.metaData);
+      return value is Map<String, dynamic> ? value : null;
+    } catch (_) {
+      return null;
+    }
+  }
+
+  String _taskName(Task task) =>
+      _taskMetadata(task)?['name'] as String? ?? task.displayName;
+
+  String? _taskOrganization(Task task) =>
+      _taskMetadata(task)?['organizationId'] as String?;
+
   Future<void> _deleteStagedFile(Task task) async {
     final file = File(await task.filePath());
     if (await file.exists()) await file.delete();
@@ -218,9 +261,14 @@ class UploadController extends ChangeNotifier {
     }
     final token = await _tokens.read();
     if (token == null) throw StateError('Your session has expired');
+    final organizationId = await _tokens.readOrganization();
+    if (organizationId == null) throw StateError('Select an organization');
     final retried = original.copyWith(
       taskId: DateTime.now().microsecondsSinceEpoch.toString(),
-      headers: {'Authorization': 'Bearer $token'},
+      headers: {
+        'Authorization': 'Bearer $token',
+        'X-Organization-Id': organizationId,
+      },
       creationTime: DateTime.now(),
       retriesRemaining: original.retries,
     );
diff --git a/lib/main.dart b/lib/main.dart
index 5161b1d..72814b1 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -73,7 +73,9 @@ class WhatsDriveApp extends StatelessWidget {
           builder: (context, session, _) => switch (session.status) {
             SessionStatus.loading => const SplashScreen(),
             SessionStatus.signedOut => const LoginScreen(),
-            SessionStatus.signedIn => const DriveScreen(),
+            SessionStatus.signedIn => DriveScreen(
+              key: ValueKey(session.organizationId),
+            ),
           },
         ),
       ),
diff --git a/lib/models/user_profile.dart b/lib/models/user_profile.dart
index fc10eb1..9e357b7 100644
--- a/lib/models/user_profile.dart
+++ b/lib/models/user_profile.dart
@@ -7,6 +7,7 @@ class UserProfile {
     required this.email,
     required this.gender,
     required this.age,
+    this.memberships = const [],
   });
 
   final String id;
@@ -16,6 +17,14 @@ class UserProfile {
   final String email;
   final String gender;
   final int age;
+  final List<OrganizationMembership> memberships;
+
+  List<OrganizationMembership> get approvedMemberships => memberships
+      .where(
+        (item) =>
+            item.status == 'APPROVED' && item.organization.status == 'ACTIVE',
+      )
+      .toList();
 
   factory UserProfile.fromJson(Map<String, dynamic> json) => UserProfile(
     id: json['id'] as String,
@@ -25,5 +34,53 @@ class UserProfile {
     email: json['email'] as String,
     gender: json['gender'] as String,
     age: json['age'] as int,
+    memberships: (json['memberships'] as List? ?? const [])
+        .map((item) => OrganizationMembership.fromJson(item))
+        .toList(),
   );
 }
+
+class OrganizationSummary {
+  const OrganizationSummary({
+    required this.id,
+    required this.code,
+    required this.name,
+    required this.status,
+  });
+  final String id;
+  final String code;
+  final String name;
+  final String status;
+
+  factory OrganizationSummary.fromJson(Map<String, dynamic> json) =>
+      OrganizationSummary(
+        id: json['id'] as String,
+        code: json['code'] as String,
+        name: json['name'] as String,
+        status: json['status'] as String,
+      );
+}
+
+class OrganizationMembership {
+  const OrganizationMembership({
+    required this.id,
+    required this.role,
+    required this.status,
+    required this.organization,
+    this.rejectionReason,
+  });
+  final String id;
+  final String role;
+  final String status;
+  final String? rejectionReason;
+  final OrganizationSummary organization;
+
+  factory OrganizationMembership.fromJson(Map<String, dynamic> json) =>
+      OrganizationMembership(
+        id: json['id'] as String,
+        role: json['role'] as String,
+        status: json['status'] as String,
+        rejectionReason: json['rejectionReason'] as String?,
+        organization: OrganizationSummary.fromJson(json['organization']),
+      );
+}
diff --git a/lib/screens/drive_screen.dart b/lib/screens/drive_screen.dart
index 7cde612..8ebe68a 100644
--- a/lib/screens/drive_screen.dart
+++ b/lib/screens/drive_screen.dart
@@ -44,6 +44,9 @@ class _DriveScreenState extends State<DriveScreen> {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
+    context.read<UploadController>().selectOrganization(
+      context.read<SessionController>().organizationId,
+    );
     final controller = context.read<UploadController>();
     if (_uploadController == controller) return;
     _uploadController?.removeListener(_onUploadChanged);
@@ -250,7 +253,9 @@ class _DriveScreenState extends State<DriveScreen> {
 
   @override
   Widget build(BuildContext context) {
-    final user = context.watch<SessionController>().user!;
+    final session = context.watch<SessionController>();
+    final user = session.user!;
+    final membership = session.membership;
     return PopScope(
       canPop: _path.isEmpty,
       onPopInvokedWithResult: (didPop, result) {
@@ -265,11 +270,13 @@ class _DriveScreenState extends State<DriveScreen> {
             crossAxisAlignment: CrossAxisAlignment.start,
             children: [
               Text(
-                _path.isEmpty ? 'Metatron-Drive' : _path.last.name,
+                _path.isEmpty
+                    ? membership?.organization.name ?? 'Metatron-Drive'
+                    : _path.last.name,
                 style: const TextStyle(fontWeight: FontWeight.w800),
               ),
               Text(
-                'Hello, ${user.name.split(' ').first}',
+                'Hello, ${user.name.split(' ').first} • ${membership?.organization.code ?? ''}',
                 style: const TextStyle(
                   fontSize: 12,
                   fontWeight: FontWeight.normal,
@@ -279,6 +286,28 @@ class _DriveScreenState extends State<DriveScreen> {
             ],
           ),
           actions: [
+            PopupMenuButton<String>(
+              tooltip: 'Switch organization',
+              icon: const Icon(Icons.business_outlined),
+              onSelected: session.selectOrganization,
+              itemBuilder: (_) => user.approvedMemberships
+                  .map(
+                    (item) => PopupMenuItem(
+                      value: item.organization.id,
+                      child: Row(
+                        children: [
+                          if (item.organization.id == session.organizationId)
+                            const Padding(
+                              padding: EdgeInsets.only(right: 8),
+                              child: Icon(Icons.check, size: 18),
+                            ),
+                          Text(item.organization.name),
+                        ],
+                      ),
+                    ),
+                  )
+                  .toList(),
+            ),
             IconButton(
               onPressed: () => Navigator.of(context).push(
                 MaterialPageRoute(builder: (_) => const UploadHistoryScreen()),
@@ -412,6 +441,7 @@ class _DriveScreenState extends State<DriveScreen> {
                       file: _files[index],
                       token: _token,
                       api: context.read<ApiClient>(),
+                      organizationId: session.organizationId,
                       onDelete: () => _deleteFile(_files[index]),
                     ),
                   ),
@@ -457,6 +487,15 @@ class _DriveScreenState extends State<DriveScreen> {
               style: const TextStyle(color: Colors.black54),
             ),
             const SizedBox(height: 22),
+            OutlinedButton.icon(
+              onPressed: () {
+                Navigator.pop(sheetContext);
+                _joinOrganization();
+              },
+              icon: const Icon(Icons.group_add_outlined),
+              label: const Text('Join another organization'),
+            ),
+            const SizedBox(height: 8),
             OutlinedButton.icon(
               onPressed: () {
                 Navigator.pop(sheetContext);
@@ -481,6 +520,56 @@ class _DriveScreenState extends State<DriveScreen> {
     );
   }
 
+  Future<void> _joinOrganization() async {
+    final code = TextEditingController();
+    final submitted = await showDialog<bool>(
+      context: context,
+      builder: (dialogContext) => AlertDialog(
+        title: const Text('Join an organization'),
+        content: TextField(
+          controller: code,
+          textCapitalization: TextCapitalization.characters,
+          decoration: const InputDecoration(labelText: 'Organization code'),
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(dialogContext, false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(dialogContext, true),
+            child: const Text('Submit request'),
+          ),
+        ],
+      ),
+    );
+    if (submitted != true || !mounted) {
+      code.dispose();
+      return;
+    }
+    try {
+      final message = await context.read<ApiClient>().joinOrganization(
+        code.text.trim().toUpperCase(),
+      );
+      if (mounted) {
+        await context.read<SessionController>().refreshProfile();
+        if (mounted) {
+          ScaffoldMessenger.of(
+            context,
+          ).showSnackBar(SnackBar(content: Text(message)));
+        }
+      }
+    } catch (error) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(context.read<ApiClient>().messageFrom(error))),
+        );
+      }
+    } finally {
+      code.dispose();
+    }
+  }
+
   Future<void> _confirmAccountDeletion() async {
     final password = TextEditingController();
     final confirmed = await showDialog<bool>(
@@ -668,11 +757,13 @@ class _FileCard extends StatelessWidget {
     required this.file,
     required this.token,
     required this.api,
+    required this.organizationId,
     required this.onDelete,
   });
   final DriveFile file;
   final String? token;
   final ApiClient api;
+  final String? organizationId;
   final VoidCallback onDelete;
   @override
   Widget build(BuildContext context) => Card(
@@ -686,7 +777,10 @@ class _FileCard extends StatelessWidget {
             child: file.isImage && token != null
                 ? Image.network(
                     api.contentUrl(file.id),
-                    headers: {'Authorization': 'Bearer $token'},
+                    headers: {
+                      'Authorization': 'Bearer $token',
+                      ..._organizationHeader(organizationId),
+                    },
                     fit: BoxFit.cover,
                     errorBuilder: (_, _, _) =>
                         const Icon(Icons.broken_image_outlined, size: 42),
@@ -741,6 +835,9 @@ class _FileCard extends StatelessWidget {
       : '${(bytes / 1024 / 1024).toStringAsFixed(1)} MB';
 }
 
+Map<String, String> _organizationHeader(String? organizationId) =>
+    organizationId == null ? const {} : {'X-Organization-Id': organizationId};
+
 class _UploadStrip extends StatelessWidget {
   const _UploadStrip();
   @override
diff --git a/lib/screens/register_screen.dart b/lib/screens/register_screen.dart
index 39f5af6..56bd91c 100644
--- a/lib/screens/register_screen.dart
+++ b/lib/screens/register_screen.dart
@@ -12,6 +12,7 @@ class RegisterScreen extends StatefulWidget {
 class _RegisterScreenState extends State<RegisterScreen> {
   final _form = GlobalKey<FormState>();
   final _name = TextEditingController();
+  final _organizationCode = TextEditingController();
   final _username = TextEditingController();
   final _email = TextEditingController();
   final _phone = TextEditingController();
@@ -20,7 +21,14 @@ class _RegisterScreenState extends State<RegisterScreen> {
 
   @override
   void dispose() {
-    for (final value in [_name, _username, _email, _phone, _password]) {
+    for (final value in [
+      _organizationCode,
+      _name,
+      _username,
+      _email,
+      _phone,
+      _password,
+    ]) {
       value.dispose();
     }
     super.dispose();
@@ -30,7 +38,8 @@ class _RegisterScreenState extends State<RegisterScreen> {
     if (!_form.currentState!.validate()) return;
     setState(() => _busy = true);
     try {
-      await context.read<SessionController>().register({
+      final message = await context.read<SessionController>().register({
+        'organizationCode': _organizationCode.text.trim().toUpperCase(),
         'name': _name.text.trim(),
         'username': _username.text.trim().toLowerCase(),
         'email': _email.text.trim().toLowerCase(),
@@ -41,7 +50,11 @@ class _RegisterScreenState extends State<RegisterScreen> {
         'gender': 'Prefer not to say',
         'password': _password.text,
       });
-      if (mounted) Navigator.of(context).popUntil((route) => route.isFirst);
+      if (mounted) {
+        final messenger = ScaffoldMessenger.of(context);
+        Navigator.of(context).popUntil((route) => route.isFirst);
+        messenger.showSnackBar(SnackBar(content: Text(message)));
+      }
     } catch (error) {
       if (mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
@@ -83,6 +96,18 @@ class _RegisterScreenState extends State<RegisterScreen> {
                       'We create your personal Google Drive folder automatically.',
                     ),
                     const SizedBox(height: 24),
+                    TextFormField(
+                      controller: _organizationCode,
+                      textCapitalization: TextCapitalization.characters,
+                      decoration: const InputDecoration(
+                        labelText: 'Organization code',
+                        prefixIcon: Icon(Icons.business_outlined),
+                      ),
+                      validator: (value) => (value?.trim().length ?? 0) < 4
+                          ? 'Enter your organization code'
+                          : null,
+                    ),
+                    const SizedBox(height: 12),
                     TextFormField(
                       controller: _name,
                       textCapitalization: TextCapitalization.words,
diff --git a/lib/services/api_client.dart b/lib/services/api_client.dart
index 9daa9a7..f20624a 100644
--- a/lib/services/api_client.dart
+++ b/lib/services/api_client.dart
@@ -17,7 +17,13 @@ class ApiClient {
       InterceptorsWrapper(
         onRequest: (options, handler) async {
           final token = await _tokens.read();
-          if (token != null) options.headers['Authorization'] = 'Bearer $token';
+          if (token != null) {
+            options.headers['Authorization'] = 'Bearer $token';
+          }
+          final organizationId = await _tokens.readOrganization();
+          if (organizationId != null) {
+            options.headers['X-Organization-Id'] = organizationId;
+          }
           handler.next(options);
         },
       ),
@@ -53,14 +59,9 @@ class ApiClient {
     );
   }
 
-  Future<({String token, UserProfile user})> register(
-    Map<String, dynamic> input,
-  ) async {
+  Future<String> register(Map<String, dynamic> input) async {
     final response = await dio.post('/auth/register', data: input);
-    return (
-      token: response.data['token'] as String,
-      user: UserProfile.fromJson(response.data['user']),
-    );
+    return response.data['message'] as String;
   }
 
   Future<UserProfile> me() async {
@@ -71,6 +72,21 @@ class ApiClient {
   Future<void> deleteAccount(String password) =>
       dio.delete('/retention/account', data: {'password': password});
 
+  Future<OrganizationSummary> lookupOrganization(String code) async {
+    final response = await dio.get(
+      '/organizations/lookup/${Uri.encodeComponent(code)}',
+    );
+    return OrganizationSummary.fromJson(response.data['organization']);
+  }
+
+  Future<String> joinOrganization(String code) async {
+    final response = await dio.post(
+      '/auth/join',
+      data: {'organizationCode': code},
+    );
+    return response.data['message'] as String;
+  }
+
   Future<List<DriveFolder>> folders(String? parentId) async {
     final response = await dio.get(
       '/folders',
diff --git a/lib/services/token_store.dart b/lib/services/token_store.dart
index 577b0bc..9f9b5c1 100644
--- a/lib/services/token_store.dart
+++ b/lib/services/token_store.dart
@@ -2,10 +2,15 @@ import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 
 class TokenStore {
   static const _tokenKey = 'auth_token';
+  static const _organizationKey = 'organization_id';
   const TokenStore();
   FlutterSecureStorage get _storage => const FlutterSecureStorage();
   Future<String?> read() => _storage.read(key: _tokenKey);
   Future<void> write(String token) =>
       _storage.write(key: _tokenKey, value: token);
   Future<void> clear() => _storage.delete(key: _tokenKey);
+  Future<String?> readOrganization() => _storage.read(key: _organizationKey);
+  Future<void> writeOrganization(String id) =>
+      _storage.write(key: _organizationKey, value: id);
+  Future<void> clearOrganization() => _storage.delete(key: _organizationKey);
 }