diff --git a/packages/moxxmpp/lib/moxxmpp.dart b/packages/moxxmpp/lib/moxxmpp.dart
index 92cd8f5..10cbb94 100644
--- a/packages/moxxmpp/lib/moxxmpp.dart
+++ b/packages/moxxmpp/lib/moxxmpp.dart
@@ -85,6 +85,7 @@ export 'package:moxxmpp/src/xeps/xep_0388/errors.dart';
 export 'package:moxxmpp/src/xeps/xep_0388/negotiators.dart';
 export 'package:moxxmpp/src/xeps/xep_0388/user_agent.dart';
 export 'package:moxxmpp/src/xeps/xep_0388/xep_0388.dart';
+export 'package:moxxmpp/src/xeps/xep_0421.dart';
 export 'package:moxxmpp/src/xeps/xep_0424.dart';
 export 'package:moxxmpp/src/xeps/xep_0444.dart';
 export 'package:moxxmpp/src/xeps/xep_0446.dart';
diff --git a/packages/moxxmpp/lib/src/managers/namespaces.dart b/packages/moxxmpp/lib/src/managers/namespaces.dart
index 713493d..bb2d241 100644
--- a/packages/moxxmpp/lib/src/managers/namespaces.dart
+++ b/packages/moxxmpp/lib/src/managers/namespaces.dart
@@ -32,3 +32,4 @@ const messageReactionsManager = 'org.moxxmpp.messagereactionsmanager';
 const stickersManager = 'org.moxxmpp.stickersmanager';
 const entityCapabilitiesManager = 'org.moxxmpp.entitycapabilities';
 const messageProcessingHintManager = 'org.moxxmpp.messageprocessinghint';
+const occupantIdManager = 'org.moxxmpp.occupantidmanager';
diff --git a/packages/moxxmpp/lib/src/namespaces.dart b/packages/moxxmpp/lib/src/namespaces.dart
index d5bd41f..e23e962 100644
--- a/packages/moxxmpp/lib/src/namespaces.dart
+++ b/packages/moxxmpp/lib/src/namespaces.dart
@@ -123,6 +123,9 @@ const sasl2Xmlns = 'urn:xmpp:sasl:2';
 // XEP-0420
 const sceXmlns = 'urn:xmpp:sce:1';
 
+// XEP-0421
+const occupantIdXmlns = 'urn:xmpp:occupant-id:0';
+
 // XEP-0422
 const fasteningXmlns = 'urn:xmpp:fasten:0';
 
diff --git a/packages/moxxmpp/lib/src/xeps/xep_0421.dart b/packages/moxxmpp/lib/src/xeps/xep_0421.dart
new file mode 100644
index 0000000..3a7c734
--- /dev/null
+++ b/packages/moxxmpp/lib/src/xeps/xep_0421.dart
@@ -0,0 +1,61 @@
+import 'dart:async';
+import 'package:moxxmpp/src/managers/base.dart';
+import 'package:moxxmpp/src/managers/data.dart';
+import 'package:moxxmpp/src/managers/handlers.dart';
+import 'package:moxxmpp/src/managers/namespaces.dart';
+import 'package:moxxmpp/src/message.dart';
+import 'package:moxxmpp/src/namespaces.dart';
+import 'package:moxxmpp/src/stanza.dart';
+import 'package:moxxmpp/src/stringxml.dart';
+
+/// Representation of a <occupant-id /> element.
+class OccupantIdData implements StanzaHandlerExtension {
+  const OccupantIdData(
+    this.id,
+  );
+
+  /// The unique occupant id.
+  final String id;
+
+  XMLNode toXML() {
+    return XMLNode.xmlns(
+      tag: 'occupant-id',
+      xmlns: occupantIdXmlns,
+      attributes: {
+        'id': id,
+      },
+    );
+  }
+}
+
+class OccupantIdManager extends XmppManagerBase {
+  OccupantIdManager() : super(occupantIdManager);
+
+  @override
+  List<String> getDiscoFeatures() => [
+        occupantIdXmlns,
+      ];
+
+  @override
+  List<StanzaHandler> getIncomingStanzaHandlers() => [
+        StanzaHandler(
+          stanzaTag: 'message',
+          tagName: 'occupant-id',
+          tagXmlns: occupantIdXmlns,
+          callback: _onMessage,
+          // Before the MessageManager
+          priority: MessageManager.messageHandlerPriority + 1,
+        ),
+      ];
+
+  @override
+  Future<bool> isSupported() async => true;
+
+  Future<StanzaHandlerData> _onMessage(
+    Stanza stanza,
+    StanzaHandlerData state,
+  ) async {
+    return state
+      ..extensions.set(OccupantIdData(stanza.attributes['id']! as String));
+  }
+}