diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 31d2fc6a21261..f2e6170416615 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -607,6 +607,7 @@
     'OCP\\IUserManager' => $baseDir . '/lib/public/IUserManager.php',
     'OCP\\IUserSession' => $baseDir . '/lib/public/IUserSession.php',
     'OCP\\Image' => $baseDir . '/lib/public/Image.php',
+    'OCP\\Install\\Events\\InstallationCompletedEvent' => $baseDir . '/lib/public/Install/Events/InstallationCompletedEvent.php',
     'OCP\\L10N\\IFactory' => $baseDir . '/lib/public/L10N/IFactory.php',
     'OCP\\L10N\\ILanguageIterator' => $baseDir . '/lib/public/L10N/ILanguageIterator.php',
     'OCP\\LDAP\\IDeletionFlagSupport' => $baseDir . '/lib/public/LDAP/IDeletionFlagSupport.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 6a2d0b10cd837..314e762fc83e5 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -656,6 +656,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OCP\\IUserManager' => __DIR__ . '/../../..' . '/lib/public/IUserManager.php',
         'OCP\\IUserSession' => __DIR__ . '/../../..' . '/lib/public/IUserSession.php',
         'OCP\\Image' => __DIR__ . '/../../..' . '/lib/public/Image.php',
+        'OCP\\Install\\Events\\InstallationCompletedEvent' => __DIR__ . '/../../..' . '/lib/public/Install/Events/InstallationCompletedEvent.php',
         'OCP\\L10N\\IFactory' => __DIR__ . '/../../..' . '/lib/public/L10N/IFactory.php',
         'OCP\\L10N\\ILanguageIterator' => __DIR__ . '/../../..' . '/lib/public/L10N/ILanguageIterator.php',
         'OCP\\LDAP\\IDeletionFlagSupport' => __DIR__ . '/../../..' . '/lib/public/LDAP/IDeletionFlagSupport.php',
diff --git a/lib/private/Setup.php b/lib/private/Setup.php
index b4102e73b5cf5..775731fbc8c51 100644
--- a/lib/private/Setup.php
+++ b/lib/private/Setup.php
@@ -22,11 +22,13 @@
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\BackgroundJob\IJobList;
 use OCP\Defaults;
+use OCP\EventDispatcher\IEventDispatcher;
 use OCP\IAppConfig;
 use OCP\IConfig;
 use OCP\IGroup;
 use OCP\IGroupManager;
 use OCP\IL10N;
+use OCP\Install\Events\InstallationCompletedEvent;
 use OCP\IRequest;
 use OCP\IUserManager;
 use OCP\IUserSession;
@@ -48,6 +50,7 @@ public function __construct(
 		protected LoggerInterface $logger,
 		protected ISecureRandom $random,
 		protected Installer $installer,
+		protected IEventDispatcher $eventDispatcher,
 	) {
 		$this->l10n = $l10nFactory->get('lib');
 	}
@@ -408,6 +411,13 @@ public function install(array $options, ?IOutput $output = null): array {
 			$user->setSystemEMailAddress($options['adminemail']);
 		}
 
+		// Dispatch installation completed event
+		$adminUsername = !empty($username) ? $username : null;
+		$adminEmail = !empty($options['adminemail']) ? $options['adminemail'] : null;
+		$this->eventDispatcher->dispatchTyped(
+			new InstallationCompletedEvent($dataDir, $adminUsername, $adminEmail)
+		);
+
 		return $error;
 	}
 
diff --git a/lib/public/Install/Events/InstallationCompletedEvent.php b/lib/public/Install/Events/InstallationCompletedEvent.php
new file mode 100644
index 0000000000000..7cf75d76d6fce
--- /dev/null
+++ b/lib/public/Install/Events/InstallationCompletedEvent.php
@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCP\Install\Events;
+
+use OCP\EventDispatcher\Event;
+
+/**
+ * Emitted when the Nextcloud installation has been completed successfully.
+ *
+ * This event is dispatched after:
+ * - The database has been configured and migrations have run
+ * - The admin user has been created (if applicable)
+ * - Default apps have been installed
+ * - Background jobs have been configured
+ * - The system has been marked as installed
+ *
+ * Apps can listen to this event to perform additional actions after installation,
+ * such as:
+ * - Sending notification emails
+ * - Triggering external APIs
+ * - Initializing app-specific data
+ * - Setting up integrations
+ *
+ * @since 33.0.0
+ */
+class InstallationCompletedEvent extends Event {
+	/**
+	 * @since 33.0.0
+	 */
+	public function __construct(
+		private string $dataDirectory,
+		private ?string $adminUsername = null,
+		private ?string $adminEmail = null,
+	) {
+		parent::__construct();
+	}
+
+	/**
+	 * Get the configured data directory path
+	 *
+	 * @since 33.0.0
+	 */
+	public function getDataDirectory(): string {
+		return $this->dataDirectory;
+	}
+
+	/**
+	 * Get the admin username if an admin user was created
+	 *
+	 * @since 33.0.0
+	 */
+	public function getAdminUsername(): ?string {
+		return $this->adminUsername;
+	}
+
+	/**
+	 * Get the admin email if configured
+	 *
+	 * @since 33.0.0
+	 */
+	public function getAdminEmail(): ?string {
+		return $this->adminEmail;
+	}
+
+	/**
+	 * Check if an admin user was created during installation
+	 *
+	 * @since 33.0.0
+	 */
+	public function hasAdminUser(): bool {
+		return $this->adminUsername !== null;
+	}
+}
diff --git a/tests/lib/Install/Events/InstallationCompletedEventTest.php b/tests/lib/Install/Events/InstallationCompletedEventTest.php
new file mode 100644
index 0000000000000..3a973e008b90b
--- /dev/null
+++ b/tests/lib/Install/Events/InstallationCompletedEventTest.php
@@ -0,0 +1,89 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\Install\Events;
+
+use OCP\Install\Events\InstallationCompletedEvent;
+
+class InstallationCompletedEventTest extends \Test\TestCase {
+	public function testConstructorWithAllParameters(): void {
+		$dataDir = '/path/to/data';
+		$adminUsername = 'admin';
+		$adminEmail = 'admin@example.com';
+
+		$event = new InstallationCompletedEvent($dataDir, $adminUsername, $adminEmail);
+
+		$this->assertEquals($dataDir, $event->getDataDirectory());
+		$this->assertEquals($adminUsername, $event->getAdminUsername());
+		$this->assertEquals($adminEmail, $event->getAdminEmail());
+		$this->assertTrue($event->hasAdminUser());
+	}
+
+	public function testConstructorWithMinimalParameters(): void {
+		$dataDir = '/path/to/data';
+
+		$event = new InstallationCompletedEvent($dataDir);
+
+		$this->assertEquals($dataDir, $event->getDataDirectory());
+		$this->assertNull($event->getAdminUsername());
+		$this->assertNull($event->getAdminEmail());
+		$this->assertFalse($event->hasAdminUser());
+	}
+
+	public function testConstructorWithUsernameOnly(): void {
+		$dataDir = '/path/to/data';
+		$adminUsername = 'admin';
+
+		$event = new InstallationCompletedEvent($dataDir, $adminUsername);
+
+		$this->assertEquals($dataDir, $event->getDataDirectory());
+		$this->assertEquals($adminUsername, $event->getAdminUsername());
+		$this->assertNull($event->getAdminEmail());
+		$this->assertTrue($event->hasAdminUser());
+	}
+
+	public function testConstructorWithUsernameAndEmail(): void {
+		$dataDir = '/path/to/data';
+		$adminUsername = 'admin';
+		$adminEmail = 'admin@example.com';
+
+		$event = new InstallationCompletedEvent($dataDir, $adminUsername, $adminEmail);
+
+		$this->assertEquals($dataDir, $event->getDataDirectory());
+		$this->assertEquals($adminUsername, $event->getAdminUsername());
+		$this->assertEquals($adminEmail, $event->getAdminEmail());
+		$this->assertTrue($event->hasAdminUser());
+	}
+
+	public function testHasAdminUserReturnsFalseWhenUsernameIsNull(): void {
+		$event = new InstallationCompletedEvent('/path/to/data', null, 'admin@example.com');
+
+		$this->assertFalse($event->hasAdminUser());
+		$this->assertNull($event->getAdminUsername());
+		$this->assertEquals('admin@example.com', $event->getAdminEmail());
+	}
+
+	public function testDataDirectoryCanBeAnyString(): void {
+		$customPath = '/custom/data/directory';
+		$event = new InstallationCompletedEvent($customPath);
+
+		$this->assertEquals($customPath, $event->getDataDirectory());
+	}
+
+	public function testEmailCanBeSetWithoutUsername(): void {
+		$dataDir = '/path/to/data';
+		$email = 'admin@example.com';
+
+		$event = new InstallationCompletedEvent($dataDir, null, $email);
+
+		$this->assertNull($event->getAdminUsername());
+		$this->assertEquals($email, $event->getAdminEmail());
+		$this->assertFalse($event->hasAdminUser());
+	}
+}
diff --git a/tests/lib/SetupTest.php b/tests/lib/SetupTest.php
index b5e1b7000c339..5e7db440c0a48 100644
--- a/tests/lib/SetupTest.php
+++ b/tests/lib/SetupTest.php
@@ -12,6 +12,7 @@
 use OC\Setup;
 use OC\SystemConfig;
 use OCP\Defaults;
+use OCP\EventDispatcher\IEventDispatcher;
 use OCP\IL10N;
 use OCP\L10N\IFactory as IL10NFactory;
 use OCP\Security\ISecureRandom;
@@ -27,6 +28,7 @@ class SetupTest extends \Test\TestCase {
 	protected LoggerInterface $logger;
 	protected ISecureRandom $random;
 	protected Installer $installer;
+	protected IEventDispatcher $eventDispatcher;
 
 	protected function setUp(): void {
 		parent::setUp();
@@ -41,9 +43,10 @@ protected function setUp(): void {
 		$this->logger = $this->createMock(LoggerInterface::class);
 		$this->random = $this->createMock(ISecureRandom::class);
 		$this->installer = $this->createMock(Installer::class);
+		$this->eventDispatcher = $this->createMock(IEventDispatcher::class);
 		$this->setupClass = $this->getMockBuilder(Setup::class)
 			->setMethods(['class_exists', 'is_callable', 'getAvailableDbDriversForPdo'])
-			->setConstructorArgs([$this->config, $this->iniWrapper, $this->l10nFactory, $this->defaults, $this->logger, $this->random, $this->installer])
+			->setConstructorArgs([$this->config, $this->iniWrapper, $this->l10nFactory, $this->defaults, $this->logger, $this->random, $this->installer, $this->eventDispatcher])
 			->getMock();
 	}