diff --git a/appinfo/info.xml b/appinfo/info.xml
index e88217fe344..5ae2f875bf8 100644
--- a/appinfo/info.xml
+++ b/appinfo/info.xml
@@ -18,7 +18,7 @@
 * 🌉 **Sync with other chat solutions** With [Matterbridge](https://github.com/42wim/matterbridge/) being integrated in Talk, you can easily sync a lot of other chat solutions to Nextcloud Talk and vice-versa.
 ]]></description>
 
-	<version>21.0.0-dev.2</version>
+	<version>21.0.0-dev.3</version>
 	<licence>agpl</licence>
 
 	<author>Anna Larch</author>
@@ -66,6 +66,7 @@
 		<job>OCA\Talk\BackgroundJob\CheckTurnCertificate</job>
 		<job>OCA\Talk\BackgroundJob\ExpireChatMessages</job>
 		<job>OCA\Talk\BackgroundJob\ExpireSignalingMessage</job>
+		<job>OCA\Talk\BackgroundJob\LockInactiveRooms</job>
 		<job>OCA\Talk\BackgroundJob\MaximumCallDuration</job>
 		<job>OCA\Talk\BackgroundJob\Reminder</job>
 		<job>OCA\Talk\BackgroundJob\RemoveEmptyRooms</job>
diff --git a/docs/settings.md b/docs/settings.md
index dc2cfe836c1..b828fe2cf33 100644
--- a/docs/settings.md
+++ b/docs/settings.md
@@ -113,3 +113,5 @@ Legend:
 | `conversations_files`                | string<br>`1` or `0`                                             | `1`        | No   | 🖌️    | Whether the files app integration is enabled allowing to start conversations in the right sidebar                                                                                                                                                                                |
 | `conversations_files_public_shares`  | string<br>`1` or `0`                                             | `1`        | No   | 🖌️    | Whether the public share integration is enabled allowing to start conversations in the right sidebar on the public share page (Requires `conversations_files` also to be enabled)                                                                                                |
 | `enable_matterbridge`                | string<br>`1` or `0`                                             | `0`        | No   | 🖌️    | Whether the Matterbridge integration is enabled and can be configured                                                                                                                                                                                                            |
+| `inactivity_lock_after_days`         | int                                                              | `0`        | No   |        | A duration (in days) after which rooms are locked. Calculated from the last activity in the room.                                                                                                                                                                                |
+| `inactivity_enable_lobby`            | string<br>`1` or `0`                                             | `0`        | No   |        | Additionally enable the lobby for inactive rooms so they can only be read by moderators.                                                                                                                                                                                         |
diff --git a/lib/BackgroundJob/LockInactiveRooms.php b/lib/BackgroundJob/LockInactiveRooms.php
new file mode 100644
index 00000000000..ae30df4c306
--- /dev/null
+++ b/lib/BackgroundJob/LockInactiveRooms.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Talk\BackgroundJob;
+
+use OCA\Talk\Config;
+use OCA\Talk\Room;
+use OCA\Talk\Service\RoomService;
+use OCA\Talk\Webinary;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\IJob;
+use OCP\BackgroundJob\TimedJob;
+use Psr\Log\LoggerInterface;
+
+class LockInactiveRooms extends TimedJob {
+
+	public function __construct(
+		ITimeFactory $timeFactory,
+		private RoomService $roomService,
+		private Config $appConfig,
+		private LoggerInterface $logger,
+	) {
+		parent::__construct($timeFactory);
+
+		// Every hour
+		$this->setInterval(60 * 60 * 24);
+		$this->setTimeSensitivity(IJob::TIME_SENSITIVE);
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function run($argument): void {
+		$interval = $this->appConfig->getInactiveLockTime();
+		$forceLobby = $this->appConfig->enableLobbyOnLockedRooms();
+		if ($interval === 0) {
+			return;
+		}
+		$timestamp = $this->time->getTime() - $interval * 60 * 60 * 24;
+		$time = $this->time->getDateTime('@' . $timestamp);
+		$rooms = $this->roomService->getInactiveRooms($time);
+		array_map(function (Room $room) use ($forceLobby) {
+			$this->roomService->setReadOnly($room, Room::READ_ONLY);
+			$this->logger->debug("Locking room {$room->getId()} due to inactivity");
+			if ($forceLobby) {
+				$this->roomService->setLobby($room, Webinary::LOBBY_NON_MODERATORS, $this->time->getDateTime());
+				$this->logger->debug("Enabling lobby for room {$room->getId()}");
+			}
+		}, $rooms);
+	}
+}
diff --git a/lib/Config.php b/lib/Config.php
index 87f26c52cd5..ccf88382bc2 100644
--- a/lib/Config.php
+++ b/lib/Config.php
@@ -694,4 +694,15 @@ public function getBlurVirtualBackground(?string $userId): bool {
 		}
 		return false;
 	}
+
+	/**
+	 * User setting falling back to admin defined app config
+	 */
+	public function getInactiveLockTime(): int {
+		return $this->appConfig->getAppValueInt('inactivity_lock_after_days');
+	}
+
+	public function enableLobbyOnLockedRooms(): bool {
+		return $this->appConfig->getAppValueBool('inactivity_enable_lobby');
+	}
 }
diff --git a/lib/Manager.php b/lib/Manager.php
index a0b4c7fe111..28e311a6887 100644
--- a/lib/Manager.php
+++ b/lib/Manager.php
@@ -317,6 +317,30 @@ public function getRoomsLongerActiveSince(\DateTime $maxActiveSince): array {
 		return $rooms;
 	}
 
+	/**
+	 * @return list<Room>
+	 */
+	public function getInactiveRooms(\DateTime $inactiveSince): array {
+		$query = $this->db->getQueryBuilder();
+		$helper = new SelectHelper();
+		$helper->selectRoomsTable($query);
+		$query->from('talk_rooms', 'r')
+			->andWhere($query->expr()->lte('r.last_activity', $query->createNamedParameter($inactiveSince, IQueryBuilder::PARAM_DATETIME_MUTABLE)))
+			->andWhere($query->expr()->neq('r.read_only', $query->createNamedParameter(Room::READ_ONLY, IQueryBuilder::PARAM_INT)))
+			->andWhere($query->expr()->in('r.type', $query->createNamedParameter([Room::TYPE_PUBLIC, Room::TYPE_GROUP], IQueryBuilder::PARAM_INT_ARRAY)))
+			->andWhere($query->expr()->emptyString('remoteServer'))
+			->orderBy('r.id', 'ASC');
+		$result = $query->executeQuery();
+
+		$rooms = [];
+		while ($row = $result->fetch()) {
+			$rooms[] = $this->createRoomObject($row);
+		}
+		$result->closeCursor();
+
+		return $rooms;
+	}
+
 	/**
 	 * @param string $userId
 	 * @param array $sessionIds A list of talk sessions to consider for loading (otherwise no session is loaded)
diff --git a/lib/Service/RoomService.php b/lib/Service/RoomService.php
index a813e906596..82e7e70ae7e 100644
--- a/lib/Service/RoomService.php
+++ b/lib/Service/RoomService.php
@@ -1212,4 +1212,11 @@ public function deleteRoom(Room $room): void {
 			));
 		}
 	}
+
+	/**
+	 * @return list<Room>
+	 */
+	public function getInactiveRooms(\DateTime $inactiveSince): array {
+		return $this->manager->getInactiveRooms($inactiveSince);
+	}
 }
diff --git a/tests/php/BackgroundJob/LockInactiveRoomsTest.php b/tests/php/BackgroundJob/LockInactiveRoomsTest.php
new file mode 100644
index 00000000000..4a3662af5ee
--- /dev/null
+++ b/tests/php/BackgroundJob/LockInactiveRoomsTest.php
@@ -0,0 +1,153 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Talk\Tests\BackgroundJob;
+
+use OCA\Talk\BackgroundJob\LockInactiveRooms;
+use OCA\Talk\Config;
+use OCA\Talk\Room;
+use OCA\Talk\Service\RoomService;
+use OCP\AppFramework\Utility\ITimeFactory;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+use Test\TestCase;
+
+class LockInactiveRoomsTest extends TestCase {
+	protected ITimeFactory&MockObject $timeFactory;
+	protected RoomService&MockObject $roomService;
+	private Config&MockObject $appConfig;
+	protected LoggerInterface&MockObject $logger;
+	private LockInactiveRooms $job;
+
+	public function setUp(): void {
+		parent::setUp();
+
+		$this->timeFactory = $this->createMock(ITimeFactory::class);
+		$this->roomService = $this->createMock(RoomService::class);
+		$this->appConfig = $this->createMock(Config::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->job = new LockInactiveRooms($this->timeFactory,
+			$this->roomService,
+			$this->appConfig,
+			$this->logger
+		);
+	}
+
+	public function testNotEnabled(): void {
+		$this->appConfig->expects(self::once())
+			->method('getInactiveLockTime')
+			->willReturn(0);
+		$this->appConfig->expects(self::once())
+			->method('enableLobbyOnLockedRooms')
+			->willReturn(false);
+		$this->timeFactory->expects(self::never())
+			->method(self::anything());
+		$this->roomService->expects(self::never())
+			->method(self::anything());
+		$this->logger->expects(self::never())
+			->method(self::anything());
+
+		$this->job->run('t');
+	}
+
+	public function testNoRooms(): void {
+		$this->appConfig->expects(self::once())
+			->method('getInactiveLockTime')
+			->willReturn(123);
+		$this->appConfig->expects(self::once())
+			->method('enableLobbyOnLockedRooms')
+			->willReturn(false);
+		$this->timeFactory->expects(self::once())
+			->method('getTime');
+		$this->timeFactory->expects(self::once())
+			->method('getDateTime');
+		$this->roomService->expects(self::once())
+			->method('getInactiveRooms')
+			->willReturn([]);
+		$this->roomService->expects(self::never())
+			->method('setReadOnly');
+		$this->roomService->expects(self::never())
+			->method('setLobby');
+		$this->logger->expects(self::never())
+			->method(self::anything());
+
+		$this->job->run('t');
+
+	}
+
+	public function testLockRooms(): void {
+		$rooms = [
+			$this->createConfiguredMock(Room::class, [
+				'getReadOnly' => 0,
+				'getType' => Room::TYPE_PUBLIC,
+			]),
+			$this->createConfiguredMock(Room::class, [
+				'getReadOnly' => 0,
+				'getType' => Room::TYPE_GROUP,
+			]),
+		];
+
+		$this->appConfig->expects(self::once())
+			->method('getInactiveLockTime')
+			->willReturn(123);
+		$this->appConfig->expects(self::once())
+			->method('enableLobbyOnLockedRooms')
+			->willReturn(false);
+		$this->timeFactory->expects(self::once())
+			->method('getTime');
+		$this->timeFactory->expects(self::once())
+			->method('getDateTime');
+		$this->roomService->expects(self::once())
+			->method('getInactiveRooms')
+			->willReturn($rooms);
+		$this->roomService->expects(self::exactly(2))
+			->method('setReadOnly');
+		$this->roomService->expects(self::never())
+			->method('setLobby');
+		$this->logger->expects(self::exactly(2))
+			->method('debug');
+
+		$this->job->run('t');
+
+	}
+
+	public function testLockRoomsAndEnableLobby(): void {
+		$rooms = [
+			$this->createConfiguredMock(Room::class, [
+				'getReadOnly' => 0,
+				'getType' => Room::TYPE_PUBLIC,
+			]),
+			$this->createConfiguredMock(Room::class, [
+				'getReadOnly' => 0,
+				'getType' => Room::TYPE_GROUP,
+			]),
+		];
+
+		$this->appConfig->expects(self::once())
+			->method('getInactiveLockTime')
+			->willReturn(123);
+		$this->appConfig->expects(self::once())
+			->method('enableLobbyOnLockedRooms')
+			->willReturn(true);
+		$this->timeFactory->expects(self::once())
+			->method('getTime');
+		$this->timeFactory->expects(self::any())
+			->method('getDateTime');
+		$this->roomService->expects(self::once())
+			->method('getInactiveRooms')
+			->willReturn($rooms);
+		$this->roomService->expects(self::exactly(2))
+			->method('setReadOnly');
+		$this->roomService->expects(self::exactly(2))
+			->method('setLobby');
+		$this->logger->expects(self::exactly(4))
+			->method('debug');
+
+		$this->job->run('t');
+	}
+}