diff --git a/backend/app/api/__init__.py b/backend/app/api/__init__.py
index 2cfe196..644583b 100644
--- a/backend/app/api/__init__.py
+++ b/backend/app/api/__init__.py
@@ -2,4 +2,4 @@ from flask import Blueprint
 
 api_bp = Blueprint('api', __name__, url_prefix='/api')
 
-from app.api import auth, users, files, calendar, contacts, email, office, passwords  # noqa: E402, F401
+from app.api import auth, users, files, calendar, contacts, email, office, passwords, backup  # noqa: E402, F401
diff --git a/backend/app/api/backup.py b/backend/app/api/backup.py
new file mode 100644
index 0000000..f1367fe
--- /dev/null
+++ b/backend/app/api/backup.py
@@ -0,0 +1,355 @@
+import io
+import json
+import os
+import shutil
+import sqlite3
+import tempfile
+import uuid
+import zipfile
+from datetime import datetime, timezone
+from pathlib import Path
+
+from flask import request, jsonify, current_app, Response
+
+from app.api import api_bp
+from app.api.auth import admin_required
+from app.extensions import db
+
+
+# Store active chunked uploads in memory (upload_id -> metadata)
+_active_uploads = {}
+
+
+# --- Backup ---
+
+@api_bp.route('/admin/backup', methods=['POST'])
+@admin_required
+def create_backup():
+    """Create a full backup as streaming ZIP download.
+
+    Contains:
+    - metadata.json (version, timestamp, stats)
+    - database.sqlite3 (copy of the SQLite DB)
+    - files/ (all uploaded user files)
+    """
+    db_uri = current_app.config['SQLALCHEMY_DATABASE_URI']
+    db_path = db_uri.replace('sqlite:///', '')
+    upload_path = Path(current_app.config['UPLOAD_PATH'])
+
+    # Gather stats
+    from app.models.user import User
+    from app.models.file import File
+    user_count = User.query.count()
+    file_count = File.query.filter_by(is_folder=False).count()
+
+    metadata = {
+        'version': '1.0',
+        'created_at': datetime.now(timezone.utc).isoformat(),
+        'user_count': user_count,
+        'file_count': file_count,
+        'description': 'Mini-Cloud Full Backup',
+    }
+
+    def generate_zip():
+        """Stream ZIP file in chunks."""
+        # We create the ZIP in a temp file to handle large data
+        with tempfile.NamedTemporaryFile(delete=False, suffix='.zip') as tmp:
+            tmp_path = tmp.name
+
+        try:
+            with zipfile.ZipFile(tmp_path, 'w', zipfile.ZIP_DEFLATED,
+                                 allowZip64=True) as zf:
+                # 1. Metadata
+                zf.writestr('metadata.json', json.dumps(metadata, indent=2))
+
+                # 2. SQLite database (safe copy via backup API)
+                db_backup_path = tmp_path + '.db'
+                try:
+                    source = sqlite3.connect(db_path)
+                    dest = sqlite3.connect(db_backup_path)
+                    source.backup(dest)
+                    source.close()
+                    dest.close()
+                    zf.write(db_backup_path, 'database.sqlite3')
+                finally:
+                    if os.path.exists(db_backup_path):
+                        os.unlink(db_backup_path)
+
+                # 3. User files
+                if upload_path.exists():
+                    for file_path in upload_path.rglob('*'):
+                        if file_path.is_file():
+                            arcname = 'files/' + str(file_path.relative_to(upload_path))
+                            zf.write(str(file_path), arcname)
+
+            # Stream the ZIP file in 1MB chunks
+            with open(tmp_path, 'rb') as f:
+                while True:
+                    chunk = f.read(1024 * 1024)
+                    if not chunk:
+                        break
+                    yield chunk
+        finally:
+            if os.path.exists(tmp_path):
+                os.unlink(tmp_path)
+
+    timestamp = datetime.now().strftime('%Y%m%d_%H%M%S')
+    filename = f'minicloud_backup_{timestamp}.zip'
+
+    return Response(
+        generate_zip(),
+        mimetype='application/zip',
+        headers={
+            'Content-Disposition': f'attachment; filename="{filename}"',
+            'X-Accel-Buffering': 'no',
+        },
+    )
+
+
+# --- Chunked Restore Upload ---
+
+@api_bp.route('/admin/restore/init', methods=['POST'])
+@admin_required
+def restore_init():
+    """Initialize a chunked restore upload.
+
+    Returns an upload_id to use for subsequent chunk uploads.
+    """
+    data = request.get_json() or {}
+    total_size = data.get('total_size', 0)
+    total_chunks = data.get('total_chunks', 0)
+    filename = data.get('filename', 'backup.zip')
+
+    upload_id = str(uuid.uuid4())
+    upload_dir = Path(tempfile.gettempdir()) / f'minicloud_restore_{upload_id}'
+    upload_dir.mkdir(parents=True, exist_ok=True)
+
+    _active_uploads[upload_id] = {
+        'dir': str(upload_dir),
+        'total_size': total_size,
+        'total_chunks': total_chunks,
+        'received_chunks': set(),
+        'filename': filename,
+        'created_at': datetime.now(timezone.utc).isoformat(),
+    }
+
+    return jsonify({
+        'upload_id': upload_id,
+        'chunk_size': 10 * 1024 * 1024,  # 10 MB recommended chunk size
+    }), 200
+
+
+@api_bp.route('/admin/restore/chunk', methods=['POST'])
+@admin_required
+def restore_chunk():
+    """Upload a single chunk of the backup file."""
+    upload_id = request.form.get('upload_id', '')
+    chunk_number = int(request.form.get('chunk_number', 0))
+
+    if upload_id not in _active_uploads:
+        return jsonify({'error': 'Upload-ID unbekannt. Bitte neu starten.'}), 404
+
+    if 'chunk' not in request.files:
+        return jsonify({'error': 'Kein Chunk gesendet'}), 400
+
+    upload_info = _active_uploads[upload_id]
+    upload_dir = Path(upload_info['dir'])
+
+    chunk_file = request.files['chunk']
+    chunk_path = upload_dir / f'chunk_{chunk_number:06d}'
+    chunk_file.save(str(chunk_path))
+
+    upload_info['received_chunks'].add(chunk_number)
+
+    return jsonify({
+        'chunk_number': chunk_number,
+        'received': len(upload_info['received_chunks']),
+        'total': upload_info['total_chunks'],
+    }), 200
+
+
+@api_bp.route('/admin/restore/finalize', methods=['POST'])
+@admin_required
+def restore_finalize():
+    """Assemble chunks and perform the restore."""
+    data = request.get_json() or {}
+    upload_id = data.get('upload_id', '')
+
+    if upload_id not in _active_uploads:
+        return jsonify({'error': 'Upload-ID unbekannt'}), 404
+
+    upload_info = _active_uploads[upload_id]
+    upload_dir = Path(upload_info['dir'])
+
+    try:
+        # Assemble chunks into ZIP
+        zip_path = upload_dir / 'backup.zip'
+        with open(str(zip_path), 'wb') as outfile:
+            chunk_num = 0
+            while True:
+                chunk_path = upload_dir / f'chunk_{chunk_num:06d}'
+                if not chunk_path.exists():
+                    break
+                with open(str(chunk_path), 'rb') as cf:
+                    shutil.copyfileobj(cf, outfile)
+                chunk_num += 1
+
+        if chunk_num == 0:
+            return jsonify({'error': 'Keine Chunks gefunden'}), 400
+
+        # Verify it's a valid ZIP
+        if not zipfile.is_zipfile(str(zip_path)):
+            return jsonify({'error': 'Ungueltige ZIP-Datei'}), 400
+
+        # Perform restore
+        result = _perform_restore(str(zip_path))
+
+        return jsonify(result), 200
+
+    except Exception as e:
+        return jsonify({'error': f'Restore fehlgeschlagen: {str(e)}'}), 500
+
+    finally:
+        # Cleanup
+        shutil.rmtree(str(upload_dir), ignore_errors=True)
+        _active_uploads.pop(upload_id, None)
+
+
+@api_bp.route('/admin/restore/direct', methods=['POST'])
+@admin_required
+def restore_direct():
+    """Direct restore from a small backup file (non-chunked, for files < 500MB)."""
+    if 'file' not in request.files:
+        return jsonify({'error': 'Keine Datei gesendet'}), 400
+
+    backup_file = request.files['file']
+
+    with tempfile.NamedTemporaryFile(delete=False, suffix='.zip') as tmp:
+        backup_file.save(tmp.name)
+        tmp_path = tmp.name
+
+    try:
+        if not zipfile.is_zipfile(tmp_path):
+            return jsonify({'error': 'Ungueltige ZIP-Datei'}), 400
+
+        result = _perform_restore(tmp_path)
+        return jsonify(result), 200
+
+    except Exception as e:
+        return jsonify({'error': f'Restore fehlgeschlagen: {str(e)}'}), 500
+    finally:
+        os.unlink(tmp_path)
+
+
+def _perform_restore(zip_path):
+    """Perform the actual restore from a validated ZIP file.
+
+    Strategy for DB merge:
+    - Open backup SQLite as a separate connection
+    - For each table in the backup, read all rows
+    - INSERT OR REPLACE into the live database
+    - This preserves any new tables/columns in the current schema
+    - Existing data with same primary keys gets overwritten by backup data
+    """
+    upload_path = Path(current_app.config['UPLOAD_PATH'])
+    stats = {'users': 0, 'files_db': 0, 'files_disk': 0, 'tables': []}
+
+    with tempfile.TemporaryDirectory() as extract_dir:
+        extract_path = Path(extract_dir)
+
+        # Extract ZIP
+        with zipfile.ZipFile(zip_path, 'r') as zf:
+            zf.extractall(str(extract_path))
+
+        # Read metadata
+        metadata_path = extract_path / 'metadata.json'
+        metadata = {}
+        if metadata_path.exists():
+            metadata = json.loads(metadata_path.read_text())
+        stats['backup_date'] = metadata.get('created_at', 'Unbekannt')
+        stats['backup_users'] = metadata.get('user_count', '?')
+        stats['backup_files'] = metadata.get('file_count', '?')
+
+        # Restore database via merge
+        backup_db_path = extract_path / 'database.sqlite3'
+        if backup_db_path.exists():
+            live_db_uri = current_app.config['SQLALCHEMY_DATABASE_URI']
+            live_db_path = live_db_uri.replace('sqlite:///', '')
+
+            backup_conn = sqlite3.connect(str(backup_db_path))
+            backup_conn.row_factory = sqlite3.Row
+            live_conn = sqlite3.connect(live_db_path)
+
+            try:
+                # Get list of tables in backup
+                backup_tables = [row[0] for row in
+                                 backup_conn.execute(
+                                     "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%'"
+                                 ).fetchall()]
+
+                # Get list of tables in live DB
+                live_tables = [row[0] for row in
+                               live_conn.execute(
+                                   "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%'"
+                               ).fetchall()]
+
+                for table in backup_tables:
+                    if table == 'alembic_version':
+                        continue
+                    if table not in live_tables:
+                        continue
+
+                    # Get column names from live table
+                    live_cols = [col[1] for col in
+                                 live_conn.execute(f'PRAGMA table_info("{table}")').fetchall()]
+                    backup_cols = [col[1] for col in
+                                   backup_conn.execute(f'PRAGMA table_info("{table}")').fetchall()]
+
+                    # Use only columns that exist in both
+                    common_cols = [c for c in backup_cols if c in live_cols]
+                    if not common_cols:
+                        continue
+
+                    cols_str = ', '.join(f'"{c}"' for c in common_cols)
+                    placeholders = ', '.join('?' for _ in common_cols)
+
+                    rows = backup_conn.execute(
+                        f'SELECT {cols_str} FROM "{table}"'
+                    ).fetchall()
+
+                    row_count = 0
+                    for row in rows:
+                        try:
+                            live_conn.execute(
+                                f'INSERT OR REPLACE INTO "{table}" ({cols_str}) VALUES ({placeholders})',
+                                tuple(row)
+                            )
+                            row_count += 1
+                        except Exception:
+                            continue
+
+                    if row_count > 0:
+                        stats['tables'].append({'name': table, 'rows': row_count})
+
+                live_conn.commit()
+            finally:
+                backup_conn.close()
+                live_conn.close()
+
+        # Restore files
+        backup_files_dir = extract_path / 'files'
+        if backup_files_dir.exists():
+            upload_path.mkdir(parents=True, exist_ok=True)
+            file_count = 0
+            for src_file in backup_files_dir.rglob('*'):
+                if src_file.is_file():
+                    rel_path = src_file.relative_to(backup_files_dir)
+                    dest = upload_path / rel_path
+                    dest.parent.mkdir(parents=True, exist_ok=True)
+                    shutil.copy2(str(src_file), str(dest))
+                    file_count += 1
+            stats['files_disk'] = file_count
+
+    stats['success'] = True
+    stats['message'] = 'Restore erfolgreich abgeschlossen'
+    return stats
diff --git a/frontend/src/views/AdminView.vue b/frontend/src/views/AdminView.vue
index 0add4a0..7bfb89c 100644
--- a/frontend/src/views/AdminView.vue
+++ b/frontend/src/views/AdminView.vue
@@ -75,6 +75,70 @@
       </div>
     </div>
 
+    <!-- Backup & Restore -->
+    <div class="admin-section">
+      <h3>Backup & Restore</h3>
+
+      <div class="backup-grid">
+        <!-- Backup -->
+        <div class="backup-card">
+          <h4><i class="pi pi-download"></i> Backup erstellen</h4>
+          <p>Erstellt eine ZIP-Datei mit der kompletten Datenbank und allen hochgeladenen Dateien.</p>
+          <Button label="Backup herunterladen" icon="pi pi-download" @click="createBackup" :loading="backupLoading" />
+        </div>
+
+        <!-- Restore -->
+        <div class="backup-card">
+          <h4><i class="pi pi-upload"></i> Restore</h4>
+
+          <div class="restore-instructions">
+            <strong>Anleitung:</strong>
+            <ol>
+              <li>Neue Mini-Cloud-Instanz aufsetzen (Docker oder manuell)</li>
+              <li>Admin-Benutzer registrieren</li>
+              <li><strong>Wichtig:</strong> In der <code>.env</code> muessen <code>SECRET_KEY</code> und <code>JWT_SECRET_KEY</code> identisch zur alten Instanz sein, sonst koennen verschluesselte Daten (E-Mail-Passwoerter, Passwort-Manager) nicht entschluesselt werden!</li>
+              <li>Backup-ZIP hier hochladen</li>
+              <li>Alle Benutzer, Dateien, Kalender, Kontakte und Einstellungen werden wiederhergestellt</li>
+            </ol>
+          </div>
+
+          <Message v-if="!restoreInProgress" severity="warn" :closable="false">
+            Die SECRET_KEY und JWT_SECRET_KEY in der .env muessen mit dem Backup uebereinstimmen!
+          </Message>
+
+          <div v-if="!restoreInProgress" class="field">
+            <label>Backup-ZIP auswaehlen</label>
+            <input ref="restoreFileInput" type="file" accept=".zip" @change="onRestoreFileSelected" />
+          </div>
+
+          <div v-if="restoreFile && !restoreInProgress" class="restore-info">
+            <p>Datei: <strong>{{ restoreFile.name }}</strong> ({{ formatSize(restoreFile.size) }})</p>
+            <Button label="Restore starten" icon="pi pi-upload" severity="warn" @click="startRestore" />
+          </div>
+
+          <div v-if="restoreInProgress" class="restore-progress">
+            <p><i class="pi pi-spin pi-spinner"></i> Restore laeuft...</p>
+            <ProgressBar :value="restoreProgress" />
+            <p class="progress-text">{{ restoreStatus }}</p>
+          </div>
+
+          <div v-if="restoreResult" class="restore-result">
+            <Message :severity="restoreResult.success ? 'success' : 'error'" :closable="false">
+              {{ restoreResult.message }}
+            </Message>
+            <div v-if="restoreResult.tables?.length" class="result-details">
+              <strong>Wiederhergestellte Tabellen:</strong>
+              <ul>
+                <li v-for="t in restoreResult.tables" :key="t.name">{{ t.name }}: {{ t.rows }} Eintraege</li>
+              </ul>
+              <p v-if="restoreResult.files_disk">Dateien auf Festplatte: {{ restoreResult.files_disk }}</p>
+              <p>Backup vom: {{ restoreResult.backup_date }}</p>
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+
     <!-- User Management -->
     <div class="admin-section">
       <div class="section-header">
@@ -257,6 +321,7 @@ import InputSwitch from 'primevue/inputswitch'
 import Message from 'primevue/message'
 import TabView from 'primevue/tabview'
 import TabPanel from 'primevue/tabpanel'
+import ProgressBar from 'primevue/progressbar'
 
 const toast = useToast()
 const auth = useAuthStore()
@@ -278,6 +343,16 @@ const smtpForm = ref({
 const smtpPasswordSet = ref(false)
 const smtpTesting = ref(false)
 
+// Backup & Restore
+const backupLoading = ref(false)
+const restoreFileInput = ref(null)
+const restoreFile = ref(null)
+const restoreInProgress = ref(false)
+const restoreProgress = ref(0)
+const restoreStatus = ref('')
+const restoreResult = ref(null)
+const CHUNK_SIZE = 10 * 1024 * 1024 // 10 MB
+
 const showUserDialog = ref(false)
 const editingUser = ref(null)
 const userForm = ref({ username: '', email: '', password: '', role: 'user', storage_quota_mb: 5120, is_active: true })
@@ -343,6 +418,124 @@ async function saveSettings() {
   }
 }
 
+// --- Backup & Restore ---
+function formatSize(bytes) {
+  if (!bytes) return '0 B'
+  const units = ['B', 'KB', 'MB', 'GB', 'TB']
+  let i = 0; let size = bytes
+  while (size >= 1024 && i < units.length - 1) { size /= 1024; i++ }
+  return `${size.toFixed(i > 0 ? 1 : 0)} ${units[i]}`
+}
+
+async function createBackup() {
+  backupLoading.value = true
+  try {
+    const response = await apiClient.post('/admin/backup', {}, { responseType: 'blob' })
+    const url = URL.createObjectURL(response.data)
+    const a = document.createElement('a')
+    a.href = url
+    const disposition = response.headers['content-disposition'] || ''
+    const match = disposition.match(/filename="?(.+?)"?$/)
+    a.download = match ? match[1] : `minicloud_backup_${new Date().toISOString().slice(0,10)}.zip`
+    a.click()
+    URL.revokeObjectURL(url)
+    toast.add({ severity: 'success', summary: 'Backup heruntergeladen', life: 3000 })
+  } catch (err) {
+    toast.add({ severity: 'error', summary: 'Backup fehlgeschlagen', detail: err.response?.data?.error, life: 5000 })
+  } finally {
+    backupLoading.value = false
+  }
+}
+
+function onRestoreFileSelected(event) {
+  restoreFile.value = event.target.files[0] || null
+  restoreResult.value = null
+}
+
+async function startRestore() {
+  if (!restoreFile.value) return
+
+  restoreInProgress.value = true
+  restoreProgress.value = 0
+  restoreStatus.value = 'Starte Upload...'
+  restoreResult.value = null
+
+  const file = restoreFile.value
+  const totalChunks = Math.ceil(file.size / CHUNK_SIZE)
+
+  try {
+    if (file.size <= 100 * 1024 * 1024) {
+      // Small file: direct upload
+      restoreStatus.value = 'Lade Datei hoch...'
+      restoreProgress.value = 50
+      const formData = new FormData()
+      formData.append('file', file)
+      const res = await apiClient.post('/admin/restore/direct', formData, {
+        headers: { 'Content-Type': 'multipart/form-data' },
+        timeout: 600000,
+      })
+      restoreProgress.value = 100
+      restoreResult.value = res.data
+    } else {
+      // Large file: chunked upload
+      // 1. Init
+      restoreStatus.value = 'Initialisiere Upload...'
+      const initRes = await apiClient.post('/admin/restore/init', {
+        total_size: file.size,
+        total_chunks: totalChunks,
+        filename: file.name,
+      })
+      const uploadId = initRes.data.upload_id
+
+      // 2. Upload chunks
+      for (let i = 0; i < totalChunks; i++) {
+        const start = i * CHUNK_SIZE
+        const end = Math.min(start + CHUNK_SIZE, file.size)
+        const chunk = file.slice(start, end)
+
+        const formData = new FormData()
+        formData.append('upload_id', uploadId)
+        formData.append('chunk_number', i.toString())
+        formData.append('chunk', chunk)
+
+        await apiClient.post('/admin/restore/chunk', formData, {
+          headers: { 'Content-Type': 'multipart/form-data' },
+          timeout: 120000,
+        })
+
+        restoreProgress.value = Math.round(((i + 1) / totalChunks) * 80)
+        restoreStatus.value = `Chunk ${i + 1} / ${totalChunks} hochgeladen (${formatSize(end)} / ${formatSize(file.size)})`
+      }
+
+      // 3. Finalize
+      restoreStatus.value = 'Stelle Daten wieder her...'
+      restoreProgress.value = 85
+      const finalRes = await apiClient.post('/admin/restore/finalize', {
+        upload_id: uploadId,
+      }, { timeout: 600000 })
+
+      restoreProgress.value = 100
+      restoreResult.value = finalRes.data
+    }
+
+    restoreStatus.value = 'Fertig!'
+    if (restoreResult.value?.success) {
+      toast.add({ severity: 'success', summary: 'Restore erfolgreich', life: 5000 })
+      await loadUsers()
+    }
+  } catch (err) {
+    restoreResult.value = {
+      success: false,
+      message: err.response?.data?.error || 'Restore fehlgeschlagen: ' + String(err),
+    }
+    toast.add({ severity: 'error', summary: 'Restore fehlgeschlagen', life: 5000 })
+  } finally {
+    restoreInProgress.value = false
+    restoreFile.value = null
+    if (restoreFileInput.value) restoreFileInput.value.value = ''
+  }
+}
+
 // --- Invite links ---
 async function createInvite() {
   inviteLoading.value = true
@@ -567,4 +760,21 @@ onMounted(() => {
 .acc-actions { display: flex; }
 .empty-hint-small { padding: 1rem; color: var(--p-text-muted-color); font-size: 0.875rem; text-align: center; }
 .section-title { margin: 1rem 0 0.5rem; font-size: 0.95rem; font-weight: 600; }
+.backup-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; }
+@media (max-width: 900px) { .backup-grid { grid-template-columns: 1fr; } }
+.backup-card { border: 1px solid var(--p-surface-200); border-radius: 8px; padding: 1.25rem; }
+.backup-card h4 { margin: 0 0 0.75rem; display: flex; align-items: center; gap: 0.5rem; }
+.backup-card p { font-size: 0.875rem; color: var(--p-text-muted-color); margin: 0 0 1rem; }
+.restore-instructions { background: var(--p-surface-50); border-radius: 6px; padding: 1rem; margin-bottom: 1rem; font-size: 0.85rem; }
+.restore-instructions ol { margin: 0.5rem 0 0; padding-left: 1.25rem; }
+.restore-instructions li { margin-bottom: 0.375rem; line-height: 1.4; }
+.restore-instructions code { background: var(--p-surface-200); padding: 0.125rem 0.375rem; border-radius: 3px; font-size: 0.8rem; }
+.restore-info { margin-top: 1rem; }
+.restore-info p { margin-bottom: 0.75rem; }
+.restore-progress { margin-top: 1rem; }
+.restore-progress p { margin: 0.5rem 0; }
+.progress-text { font-size: 0.825rem; color: var(--p-text-muted-color); }
+.restore-result { margin-top: 1rem; }
+.result-details { font-size: 0.85rem; margin-top: 0.5rem; }
+.result-details ul { margin: 0.25rem 0; padding-left: 1.25rem; }
 </style>