diff --git a/app/Console/Commands/Database/CleanupLecturers.php b/app/Console/Commands/Database/CleanupLecturers.php
new file mode 100644
index 0000000..b3a4a9d
--- /dev/null
+++ b/app/Console/Commands/Database/CleanupLecturers.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace App\Console\Commands\Database;
+
+use App\Models\Lecturer;
+use Illuminate\Console\Attributes\Description;
+use Illuminate\Console\Attributes\Signature;
+use Illuminate\Console\Command;
+use Illuminate\Support\Facades\DB;
+
+#[Signature('lecturers:cleanup {--force : Actually delete instead of doing a dry-run}')]
+#[Description('Delete lecturers without any courses or course events. Their library items and media are merged into the "Einundzwanzig" lecturer first.')]
+class CleanupLecturers extends Command
+{
+    private const MERGE_TARGET_NAME = 'Einundzwanzig';
+
+    public function handle(): int
+    {
+        $target = Lecturer::query()->where('name', self::MERGE_TARGET_NAME)->first();
+
+        if (! $target) {
+            $this->error(sprintf('Merge target lecturer "%s" not found. Aborting.', self::MERGE_TARGET_NAME));
+
+            return Command::FAILURE;
+        }
+
+        $candidates = Lecturer::query()
+            ->whereKeyNot($target->getKey())
+            ->whereDoesntHave('courses')
+            ->whereDoesntHave('coursesEvents')
+            ->get();
+
+        if ($candidates->isEmpty()) {
+            $this->info('No empty lecturers to clean up.');
+
+            return Command::SUCCESS;
+        }
+
+        $force = (bool) $this->option('force');
+
+        $this->info(sprintf(
+            '%s %d empty lecturer(s). Library items & media will be merged into "%s" (#%d).',
+            $force ? 'Deleting' : '[DRY-RUN] Would delete',
+            $candidates->count(),
+            $target->name,
+            $target->getKey(),
+        ));
+
+        if ($force && ! $this->confirm('This permanently deletes lecturers on this database. Continue?', false)) {
+            $this->warn('Aborted.');
+
+            return Command::FAILURE;
+        }
+
+        $stats = ['deleted' => 0, 'libraryItems' => 0, 'media' => 0];
+
+        $this->withProgressBar($candidates, function (Lecturer $lecturer) use ($target, $force, &$stats): void {
+            // Use ->count() (query) instead of loading the relation, so the
+            // media delete-hook on $lecturer->delete() sees an empty set after reassignment.
+            $libraryItems = $lecturer->libraryItems()->count();
+            $media = $lecturer->media()->count();
+
+            $stats['libraryItems'] += $libraryItems;
+            $stats['media'] += $media;
+            $stats['deleted']++;
+
+            if (! $force) {
+                return;
+            }
+
+            DB::transaction(function () use ($lecturer, $target): void {
+                $lecturer->libraryItems()->update(['lecturer_id' => $target->getKey()]);
+                // ponytail: reassigning model_id keeps files & model_type (both are Lecturer) intact.
+                // Ceiling: merged 'avatar' media land in the target's singleFile collection, so a later
+                // avatar upload on the target will prune them. Move them to 'images' if that matters.
+                $lecturer->media()->update(['model_id' => $target->getKey()]);
+                $lecturer->delete();
+            });
+        });
+
+        $this->newLine(2);
+        $this->table(['Metric', 'Count'], [
+            [$force ? 'Lecturers deleted' : 'Lecturers to delete', $stats['deleted']],
+            [$force ? 'Library items merged' : 'Library items to merge', $stats['libraryItems']],
+            [$force ? 'Media merged' : 'Media to merge', $stats['media']],
+        ]);
+
+        if (! $force) {
+            $this->newLine();
+            $this->comment('Dry-run only. Re-run with --force to apply.');
+        }
+
+        return Command::SUCCESS;
+    }
+}
diff --git a/app/Http/Controllers/Api/UserController.php b/app/Http/Controllers/Api/UserController.php
index db0c0ef..200e13b 100644
--- a/app/Http/Controllers/Api/UserController.php
+++ b/app/Http/Controllers/Api/UserController.php
@@ -3,6 +3,7 @@
 namespace App\Http\Controllers\Api;
 
 use App\Http\Controllers\Controller;
+use App\Models\User;
 use Dedoc\Scramble\Attributes\Group;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
@@ -18,9 +19,33 @@ class UserController extends Controller
      */
     public function __invoke(Request $request): JsonResponse
     {
-        $user = $request->user();
+        return response()->json($this->profilePayload($request->user()));
+    }
 
-        return response()->json([
+    /**
+     * Profil aktualisieren
+     *
+     * Erlaubt dem Token-Inhaber, den eigenen Anzeigenamen zu ändern.
+     * Rollen (is_lecturer/is_leader) sind bewusst NICHT änderbar.
+     */
+    public function update(Request $request): JsonResponse
+    {
+        $validated = $request->validate([
+            'name' => ['required', 'string', 'max:255'],
+        ]);
+
+        $user = $request->user();
+        $user->update(['name' => $validated['name']]);
+
+        return response()->json($this->profilePayload($user->fresh()));
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function profilePayload(User $user): array
+    {
+        return [
             'id' => $user->id,
             'name' => $user->name,
             'email' => $user->email,
@@ -28,6 +53,6 @@ class UserController extends Controller
             'is_lecturer' => (bool) $user->is_lecturer,
             'is_leader' => (bool) $user->is_leader,
             'avatar' => $user->profile_photo_url,
-        ]);
+        ];
     }
 }
diff --git a/routes/api.php b/routes/api.php
index 590b9d6..d872455 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -42,6 +42,7 @@ Route::middleware('auth:sanctum')
     ->as('api.')
     ->group(function () {
         Route::get('user', UserController::class)->name('user');
+        Route::patch('user', [UserController::class, 'update'])->name('user.update');
 
         Route::post('courses', [CourseController::class, 'store'])
             ->name('courses.store');
diff --git a/tests/Feature/Auth/MobileAuthTest.php b/tests/Feature/Auth/MobileAuthTest.php
index 7088c0e..a946692 100644
--- a/tests/Feature/Auth/MobileAuthTest.php
+++ b/tests/Feature/Auth/MobileAuthTest.php
@@ -225,6 +225,36 @@ it('denies /api/user without a token', function () {
     $this->getJson('/api/user')->assertUnauthorized();
 });
 
+it('updates the token owner display name', function () {
+    $user = User::factory()->create(['name' => 'Old Name']);
+    Sanctum::actingAs($user);
+
+    $this->patchJson('/api/user', ['name' => 'Satoshi'])
+        ->assertOk()
+        ->assertJsonPath('name', 'Satoshi');
+
+    expect($user->fresh()->name)->toBe('Satoshi');
+});
+
+it('does not let the user change roles via the profile update', function () {
+    $user = User::factory()->create(['is_lecturer' => false]);
+    Sanctum::actingAs($user);
+
+    $this->patchJson('/api/user', ['name' => 'Satoshi', 'is_lecturer' => true])
+        ->assertOk();
+
+    expect((bool) $user->fresh()->is_lecturer)->toBeFalse();
+});
+
+it('rejects an empty display name', function () {
+    $user = User::factory()->create();
+    Sanctum::actingAs($user);
+
+    $this->patchJson('/api/user', ['name' => ''])
+        ->assertUnprocessable()
+        ->assertJsonValidationErrors('name');
+});
+
 it('revokes the requesting token on mobile logout', function () {
     $user = User::factory()->create();
     $plainTextToken = $user->createToken('Pixel 10')->plainTextToken;
diff --git a/tests/Feature/Console/CleanupLecturersTest.php b/tests/Feature/Console/CleanupLecturersTest.php
new file mode 100644
index 0000000..c4271d7
--- /dev/null
+++ b/tests/Feature/Console/CleanupLecturersTest.php
@@ -0,0 +1,45 @@
+<?php
+
+use App\Models\Course;
+use App\Models\Lecturer;
+use App\Models\LibraryItem;
+
+it('aborts when the merge target is missing', function () {
+    Lecturer::factory()->create(['name' => 'Orphan']);
+
+    $this->artisan('lecturers:cleanup', ['--force' => true])->assertExitCode(1);
+
+    expect(Lecturer::query()->where('name', 'Orphan')->exists())->toBeTrue();
+});
+
+it('does nothing on a dry-run', function () {
+    Lecturer::factory()->create(['name' => 'Einundzwanzig']);
+    $empty = Lecturer::factory()->create();
+
+    $this->artisan('lecturers:cleanup')->assertExitCode(0);
+
+    expect(Lecturer::query()->find($empty->id))->not->toBeNull();
+});
+
+it('merges library items and deletes empty lecturers with --force', function () {
+    $target = Lecturer::factory()->create(['name' => 'Einundzwanzig']);
+    $empty = Lecturer::factory()->create();
+    $item = LibraryItem::factory()->create(['lecturer_id' => $empty->id]);
+
+    $this->artisan('lecturers:cleanup', ['--force' => true])
+        ->expectsConfirmation('This permanently deletes lecturers on this database. Continue?', 'yes')
+        ->assertExitCode(0);
+
+    expect(Lecturer::query()->find($empty->id))->toBeNull();
+    expect($item->fresh()->lecturer_id)->toBe($target->id);
+});
+
+it('keeps lecturers that have a course', function () {
+    Lecturer::factory()->create(['name' => 'Einundzwanzig']);
+    $withCourse = Lecturer::factory()->create();
+    Course::factory()->create(['lecturer_id' => $withCourse->id]);
+
+    $this->artisan('lecturers:cleanup', ['--force' => true])->assertExitCode(0);
+
+    expect(Lecturer::query()->find($withCourse->id))->not->toBeNull();
+});