diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e28f53..f105cb0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- German translations for password reset emails
+- JSON-based translation files (`lang/de.json`) for German language support
+- Localized password reset email template using `__()` helper functions
+- 5 comprehensive tests for password reset email translations
+- `SetLocaleFromHeader` middleware for Accept-Language header detection
+- Automatic locale switching based on HTTP Accept-Language header
+- Support for multi-language API responses (English, German)
+- 6 comprehensive tests for locale middleware functionality
 - Translation.io integration for multi-language support (en, de)
 - Configuration file `config/translation.php` for Translation.io
 - `TRANSLATIONIO_KEY` environment variable for API key management
diff --git a/app/Http/Middleware/SetLocaleFromHeader.php b/app/Http/Middleware/SetLocaleFromHeader.php
new file mode 100644
index 0000000..43316da
--- /dev/null
+++ b/app/Http/Middleware/SetLocaleFromHeader.php
@@ -0,0 +1,43 @@
+<?php
+
+// SPDX-FileCopyrightText: 2025 SecPal Contributors
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\App;
+use Symfony\Component\HttpFoundation\Response;
+
+class SetLocaleFromHeader
+{
+    /**
+     * Handle an incoming request and set the application locale based on Accept-Language header.
+     *
+     * The middleware reads the Accept-Language header from the request and sets the application
+     * locale accordingly. If no header is present or the language is not supported, it defaults
+     * to the application's configured locale.
+     *
+     * Supported locales: en (English), de (German)
+     *
+     * @param  \Closure(\Illuminate\Http\Request): (\Symfony\Component\HttpFoundation\Response)  $next
+     */
+    public function handle(Request $request, Closure $next): Response
+    {
+        $supportedLocales = ['en', 'de'];
+
+        // Get preferred language from Accept-Language header
+        $locale = $request->getPreferredLanguage($supportedLocales);
+
+        // Fall back to default if no match
+        if ($locale === null) {
+            $defaultLocale = config('app.locale');
+            $locale = is_string($defaultLocale) ? $defaultLocale : 'en';
+        }
+
+        App::setLocale($locale);
+
+        return $next($request);
+    }
+}
diff --git a/bootstrap/app.php b/bootstrap/app.php
index 405de00..f8dcb07 100644
--- a/bootstrap/app.php
+++ b/bootstrap/app.php
@@ -23,6 +23,11 @@
             'role' => \Spatie\Permission\Middleware\RoleMiddleware::class,
         ]);
 
+        // Apply SetLocaleFromHeader middleware to all API routes
+        $middleware->api(append: [
+            \App\Http\Middleware\SetLocaleFromHeader::class,
+        ]);
+
         // Define rate limiters (using cache, not Redis)
         RateLimiter::for('api', function (Request $request) {
             return Limit::perMinute(60)->by($request->user()?->id ?: $request->ip());
diff --git a/lang/.translation_io b/lang/.translation_io
new file mode 100644
index 0000000..ee0aa7d
--- /dev/null
+++ b/lang/.translation_io
@@ -0,0 +1 @@
+{"timestamp":1762116846}
diff --git a/lang/.translation_io.license b/lang/.translation_io.license
new file mode 100644
index 0000000..4f63a14
--- /dev/null
+++ b/lang/.translation_io.license
@@ -0,0 +1,2 @@
+SPDX-FileCopyrightText: 2025 SecPal Contributors
+SPDX-License-Identifier: CC0-1.0
diff --git a/lang/de.json b/lang/de.json
new file mode 100644
index 0000000..96e012f
--- /dev/null
+++ b/lang/de.json
@@ -0,0 +1,13 @@
+{
+  "Reset Your Password": "Passwort zurücksetzen",
+  "Hello": "Hallo",
+  "You requested a password reset for your SecPal account.": "Sie haben eine Passwort-Zurücksetzung für Ihr SecPal-Konto angefordert.",
+  "Click the button below to reset your password. This link will expire in :minutes minutes.": "Klicken Sie auf die Schaltfläche unten, um Ihr Passwort zurückzusetzen. Dieser Link läuft in :minutes Minuten ab.",
+  "Reset Password": "Passwort zurücksetzen",
+  "Security Notice:": "Sicherheitshinweis:",
+  "Never share this link with anyone": "Teilen Sie diesen Link niemals mit anderen",
+  "If you didn't request this reset, please ignore this email": "Wenn Sie diese Zurücksetzung nicht angefordert haben, ignorieren Sie diese E-Mail bitte",
+  "Your password will remain unchanged until you complete the reset process": "Ihr Passwort bleibt unverändert, bis Sie den Zurücksetzungsvorgang abschließen",
+  "Thanks": "Vielen Dank",
+  "If you're having trouble clicking the \":button\" button, copy and paste the URL below into your web browser:": "Falls Sie Probleme beim Klicken auf die Schaltfläche \":button\" haben, kopieren Sie die folgende URL und fügen Sie sie in Ihren Webbrowser ein:"
+}
diff --git a/lang/de.json.license b/lang/de.json.license
new file mode 100644
index 0000000..4f63a14
--- /dev/null
+++ b/lang/de.json.license
@@ -0,0 +1,2 @@
+SPDX-FileCopyrightText: 2025 SecPal Contributors
+SPDX-License-Identifier: CC0-1.0
diff --git a/resources/views/emails/password-reset.blade.php b/resources/views/emails/password-reset.blade.php
index b6bb860..f652301 100644
--- a/resources/views/emails/password-reset.blade.php
+++ b/resources/views/emails/password-reset.blade.php
@@ -4,30 +4,30 @@
 --}}
 
 <x-mail::message>
-# Reset Your Password
+# {{ __('Reset Your Password') }}
 
-Hello {{ $user->name }},
+{{ __('Hello') }} {{ $user->name }},
 
-You requested a password reset for your SecPal account.
+{{ __('You requested a password reset for your SecPal account.') }}
 
-Click the button below to reset your password. This link will expire in **{{ $expiresInMinutes }} minutes**.
+{{ __('Click the button below to reset your password. This link will expire in :minutes minutes.', ['minutes' => $expiresInMinutes]) }}
 
 <x-mail::button :url="$resetUrl">
-Reset Password
+{{ __('Reset Password') }}
 </x-mail::button>
 
-**Security Notice:**
-- Never share this link with anyone
-- If you didn't request this reset, please ignore this email
-- Your password will remain unchanged until you complete the reset process
+**{{ __('Security Notice:') }}**
+- {{ __('Never share this link with anyone') }}
+- {{ __('If you didn\'t request this reset, please ignore this email') }}
+- {{ __('Your password will remain unchanged until you complete the reset process') }}
 
-Thanks,<br>
+{{ __('Thanks') }},<br>
 {{ config('app.name') }}
 
 ---
 
 <small>
-If you're having trouble clicking the "Reset Password" button, copy and paste the URL below into your web browser:<br>
+{{ __('If you\'re having trouble clicking the ":button" button, copy and paste the URL below into your web browser:', ['button' => __('Reset Password')]) }}<br>
 {{ $resetUrl }}
 </small>
 </x-mail::message>
diff --git a/tests/Feature/LocaleMiddlewareTest.php b/tests/Feature/LocaleMiddlewareTest.php
new file mode 100644
index 0000000..898544f
--- /dev/null
+++ b/tests/Feature/LocaleMiddlewareTest.php
@@ -0,0 +1,58 @@
+<?php
+
+// SPDX-FileCopyrightText: 2025 SecPal Contributors
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use Illuminate\Support\Facades\App;
+
+test('middleware sets locale from Accept-Language header to German', function (): void {
+    $response = $this->withHeaders([
+        'Accept-Language' => 'de',
+    ])->get('/api/health');
+
+    expect(App::getLocale())->toBe('de');
+    $response->assertOk();
+});
+
+test('middleware sets locale from Accept-Language header to English', function (): void {
+    $response = $this->withHeaders([
+        'Accept-Language' => 'en',
+    ])->get('/api/health');
+
+    expect(App::getLocale())->toBe('en');
+    $response->assertOk();
+});
+
+test('middleware defaults to configured locale when no Accept-Language header', function (): void {
+    $response = $this->get('/api/health');
+
+    expect(App::getLocale())->toBe(config('app.locale'));
+    $response->assertOk();
+});
+
+test('middleware defaults to configured locale for unsupported language', function (): void {
+    $response = $this->withHeaders([
+        'Accept-Language' => 'fr',
+    ])->get('/api/health');
+
+    expect(App::getLocale())->toBe(config('app.locale'));
+    $response->assertOk();
+});
+
+test('middleware handles complex Accept-Language header with quality values', function (): void {
+    $response = $this->withHeaders([
+        'Accept-Language' => 'de-DE,de;q=0.9,en-US;q=0.8,en;q=0.7',
+    ])->get('/api/health');
+
+    expect(App::getLocale())->toBe('de');
+    $response->assertOk();
+});
+
+test('middleware prefers higher quality language from Accept-Language header', function (): void {
+    $response = $this->withHeaders([
+        'Accept-Language' => 'en;q=0.5,de;q=0.9',
+    ])->get('/api/health');
+
+    expect(App::getLocale())->toBe('de');
+    $response->assertOk();
+});
diff --git a/tests/Feature/PasswordResetEmailLocalizationTest.php b/tests/Feature/PasswordResetEmailLocalizationTest.php
new file mode 100644
index 0000000..e3fb6de
--- /dev/null
+++ b/tests/Feature/PasswordResetEmailLocalizationTest.php
@@ -0,0 +1,56 @@
+<?php
+
+// SPDX-FileCopyrightText: 2025 SecPal Contributors
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use Illuminate\Support\Facades\App;
+
+test('password reset translation strings exist in English', function (): void {
+    App::setLocale('en');
+
+    expect(__('Reset Your Password'))->toBe('Reset Your Password')
+        ->and(__('Hello'))->toBe('Hello')
+        ->and(__('Security Notice:'))->toBe('Security Notice:')
+        ->and(__('Thanks'))->toBe('Thanks')
+        ->and(__('Reset Password'))->toBe('Reset Password');
+});
+
+test('password reset translation strings exist in German', function (): void {
+    App::setLocale('de');
+
+    expect(__('Reset Your Password'))->toBe('Passwort zurücksetzen')
+        ->and(__('Hello'))->toBe('Hallo')
+        ->and(__('Security Notice:'))->toBe('Sicherheitshinweis:')
+        ->and(__('Thanks'))->toBe('Vielen Dank')
+        ->and(__('Reset Password'))->toBe('Passwort zurücksetzen');
+});
+
+test('password reset translation with parameters works in English', function (): void {
+    App::setLocale('en');
+
+    $translated = __('Click the button below to reset your password. This link will expire in :minutes minutes.', ['minutes' => 60]);
+
+    expect($translated)->toContain('60 minutes')
+        ->and($translated)->toContain('Click the button');
+});
+
+test('password reset translation with parameters works in German', function (): void {
+    App::setLocale('de');
+
+    $translated = __('Click the button below to reset your password. This link will expire in :minutes minutes.', ['minutes' => 60]);
+
+    expect($translated)->toContain('60 Minuten')
+        ->and($translated)->toContain('Klicken Sie auf die Schaltfläche');
+});
+
+test('password reset button text translation with parameters works', function (): void {
+    App::setLocale('de');
+
+    $translated = __('If you\'re having trouble clicking the ":button" button, copy and paste the URL below into your web browser:', [
+        'button' => __('Reset Password'),
+    ]);
+
+    expect($translated)
+        ->toContain('Passwort zurücksetzen')
+        ->toContain('kopieren Sie die folgende URL');
+});