diff --git a/lib/model/content.dart b/lib/model/content.dart
index 74509735aa..358a02feb1 100644
--- a/lib/model/content.dart
+++ b/lib/model/content.dart
@@ -1071,38 +1071,66 @@ class LinkNode extends InlineContainerNode {
   }
 }
 
-enum UserMentionType { user, userGroup }
+sealed class MentionNode extends InlineContainerNode {
+  const MentionNode({
+    super.debugHtmlNode,
+    required super.nodes,
+    required this.isSilent,
+  });
+
+  final bool isSilent; // TODO(#647)
 
-class UserMentionNode extends InlineContainerNode {
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(FlagProperty('isSilent', value: isSilent, ifTrue: "is silent"));
+  }
+}
+
+class UserMentionNode extends MentionNode {
   const UserMentionNode({
     super.debugHtmlNode,
     required super.nodes,
+    required super.isSilent,
     required this.userId,
-    required this.isSilent,
   });
 
   /// The ID of the user being mentioned.
   ///
-  /// This is null for wildcard mentions, user group mentions,
+  /// This is null for wildcard mentions
   /// or when the user ID is unavailable in the HTML (e.g., legacy mentions).
   final int? userId;
 
-  final bool isSilent; // TODO(#647)
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(IntProperty('userId', userId));
+  }
+}
 
-  // For the legacy design, we don't need this information in code; instead,
-  // the inner text already shows how to communicate it to the user
-  // and we show that text in the same style for all types of @-mention.
-  // We'll need these for implementing the post-2023 Zulip design, though.
-  //   final UserMentionType mentionType; // TODO(#646)
+class UserGroupMentionNode extends MentionNode {
+  const UserGroupMentionNode({
+    super.debugHtmlNode,
+    required super.nodes,
+    required super.isSilent,
+    required this.userGroupId,
+  });
+
+  /// The ID of the user group being mentioned.
+  ///
+  /// This is non-nullable because user group mentions
+  /// always have data-user-group-id.
+  final int userGroupId;
 
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
-    properties.add(IntProperty('userId', userId));
-    properties.add(FlagProperty('isSilent', value: isSilent, ifTrue: "is silent"));
+    properties.add(IntProperty('userGroupId', userGroupId));
   }
 }
 
+// TODO(#646) add WildcardMentionNode
+
 sealed class EmojiNode extends InlineContentNode {
   const EmojiNode({super.debugHtmlNode});
 }
@@ -1292,7 +1320,7 @@ class _ZulipInlineContentParser {
       debugSoftFailReason: kDebugMode ? parsed.softFailReason : null);
   }
 
-  UserMentionNode? parseUserMention(dom.Element element) {
+  MentionNode? parseMention(dom.Element element) {
     assert(element.localName == 'span');
     final debugHtmlNode = kDebugMode ? element : null;
 
@@ -1318,15 +1346,16 @@ class _ZulipInlineContentParser {
       i++;
     }
 
+    String? mentionType;
     if (i >= classes.length) return null;
     if ((classes[i] == 'topic-mention' && !hasChannelWildcardClass)
         || classes[i] == 'user-mention'
         || (classes[i] == 'user-group-mention' && !hasChannelWildcardClass)) {
       // The class we already knew we'd find before we called this function.
-      // We ignore the distinction between these; see [UserMentionNode].
-      // Also, we don't expect "user-group-mention" and "channel-wildcard-mention"
+      // We don't expect "user-group-mention" and "channel-wildcard-mention"
       // to be in the list at the same time and neither we expect "topic-mention"
       // and "channel-wildcard-mention" to be in the list at the same time.
+      mentionType = classes[i];
       i++;
     }
 
@@ -1335,21 +1364,35 @@ class _ZulipInlineContentParser {
       return null;
     }
 
-    final userId = switch (element.attributes['data-user-id']) {
-      // For legacy, user group or wildcard mentions.
-      null || '*' => null,
-      final userIdString => int.tryParse(userIdString),
-    };
-
-    // TODO assert UserMentionNode can't contain LinkNode;
+    // TODO assert MentionNode can't contain LinkNode;
     //   either a debug-mode check, or perhaps we can make expectations much
-    //   tighter on a UserMentionNode's contents overall.
+    //   tighter on a MentionNode's contents overall.
     final nodes = parseInlineContentList(element.nodes);
-    return UserMentionNode(
-      nodes: nodes,
-      userId: userId,
-      isSilent: isSilent,
-      debugHtmlNode: debugHtmlNode);
+
+    if (mentionType case 'user-group-mention') {
+      final userGroupId = int.tryParse(
+        element.attributes['data-user-group-id'] ?? '',
+        radix: 10);
+      if (userGroupId == null) {
+        return null;
+      }
+      return UserGroupMentionNode(
+        nodes: nodes,
+        isSilent: isSilent,
+        userGroupId: userGroupId,
+        debugHtmlNode: debugHtmlNode);
+    } else {
+      final userId = switch (element.attributes['data-user-id']) {
+        // For legacy or wildcard mentions.
+        null || '*' => null,
+        final userIdString => int.tryParse(userIdString, radix: 10),
+      };
+      return UserMentionNode(
+        nodes: nodes,
+        isSilent: isSilent,
+        userId: userId,
+        debugHtmlNode: debugHtmlNode);
+    }
   }
 
   /// The links found so far in the current block inline container.
@@ -1364,11 +1407,11 @@ class _ZulipInlineContentParser {
     return result;
   }
 
-  /// Matches all className values that could be a UserMentionNode,
+  /// Matches all className values that could be a subclass of MentionNode,
   /// and no className values that could be any other type of node.
   // Specifically, checks for `user-mention` or `user-group-mention`
   // or `topic-mention` as a member of the list.
-  static final _userMentionClassNameRegexp = RegExp(
+  static final _mentionClassNameRegexp = RegExp(
     r"(^| )" r"(?:user(?:-group)?|topic)-mention" r"( |$)");
 
   static final _emojiClassNameRegexp = () {
@@ -1422,8 +1465,8 @@ class _ZulipInlineContentParser {
     }
 
     if (localName == 'span'
-        && _userMentionClassNameRegexp.hasMatch(className)) {
-      return parseUserMention(element) ?? unimplemented();
+        && _mentionClassNameRegexp.hasMatch(className)) {
+      return parseMention(element) ?? unimplemented();
     }
 
     if (localName == 'span'
diff --git a/lib/widgets/content.dart b/lib/widgets/content.dart
index f0100a90f2..126f930403 100644
--- a/lib/widgets/content.dart
+++ b/lib/widgets/content.dart
@@ -1096,9 +1096,9 @@ class _InlineContentBuilder {
       case InlineCodeNode():
         return _buildInlineCode(node);
 
-      case UserMentionNode():
+      case MentionNode():
         return WidgetSpan(alignment: PlaceholderAlignment.middle,
-          child: UserMention(ambientTextStyle: widget.style, node: node));
+          child: Mention(ambientTextStyle: widget.style, node: node));
 
       case UnicodeEmojiNode():
         return TextSpan(text: node.emojiUnicode, recognizer: _recognizer,
@@ -1182,27 +1182,37 @@ class _InlineContentBuilder {
 
 const kInlineCodeFontSizeFactor = 0.825;
 
-class UserMention extends StatelessWidget {
-  const UserMention({
+class Mention extends StatelessWidget {
+  const Mention({
     super.key,
     required this.ambientTextStyle,
     required this.node,
   });
 
   final TextStyle ambientTextStyle;
-  final UserMentionNode node;
+  final MentionNode node;
 
   @override
   Widget build(BuildContext context) {
     final store = PerAccountStoreWidget.of(context);
     final contentTheme = ContentTheme.of(context);
+
     var nodes = node.nodes;
-    if (node.userId case final userId?) {
-      final user = store.getUser(userId);
-      if (user case User(:final fullName)) {
-        nodes = [TextNode(node.isSilent ? fullName : '@$fullName')];
-      }
+    switch (node) {
+      case UserGroupMentionNode(:final userGroupId):
+        final userGroup = store.getGroup(userGroupId);
+        if (userGroup case UserGroup(:final name)) {
+          // TODO(#1260) Get display name for system groups using localization
+          nodes = [TextNode(node.isSilent ? name : '@$name')];
+        }
+      case UserMentionNode(:final userId?):
+        final user = store.getUser(userId);
+        if (user case User(:final fullName)) {
+          nodes = [TextNode(node.isSilent ? fullName : '@$fullName')];
+        }
+      case UserMentionNode(userId: null):
     }
+
     return Container(
       decoration: BoxDecoration(
         // TODO(#646) different for wildcard mentions
@@ -1213,12 +1223,11 @@ class UserMention extends StatelessWidget {
         // If an @-mention is inside a link, let the @-mention override it.
         recognizer: null,  // TODO(#1867) make @-mentions tappable, for info on user
         // One hopes an @-mention can't contain an embedded link.
-        // (The parser on creating a UserMentionNode has a TODO to check that.)
+        // (The parser on creating a MentionNode has a TODO to check that.)
         linkRecognizers: null,
 
         // TODO(#647) when self-user is non-silently mentioned, make bold, and:
-        // TODO(#646) when self-user is non-silently mentioned,
-        //   distinguish font color between direct and wildcard mentions
+        // TODO(#646) distinguish font color between direct and wildcard mentions
         style: ambientTextStyle,
 
         nodes: nodes));
diff --git a/test/model/content_test.dart b/test/model/content_test.dart
index 6baa01ca86..b5da630f7e 100644
--- a/test/model/content_test.dart
+++ b/test/model/content_test.dart
@@ -111,105 +111,105 @@ class ContentExample {
     "@**Greg Price**",
     expectedText: '@Greg Price',
     '<p><span class="user-mention" data-user-id="2187">@Greg Price</span></p>',
-    const UserMentionNode(nodes: [TextNode('@Greg Price')], userId: 2187, isSilent: false));
+    const UserMentionNode(nodes: [TextNode('@Greg Price')], isSilent: false, userId: 2187));
 
   static final userMentionSilent = ContentExample.inline(
     'silent user @-mention',
     "@_**Greg Price**",
     expectedText: 'Greg Price',
     '<p><span class="user-mention silent" data-user-id="2187">Greg Price</span></p>',
-    const UserMentionNode(nodes: [TextNode('Greg Price')], userId: 2187, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('Greg Price')], isSilent: true, userId: 2187));
 
   static final userMentionSilentClassOrderReversed = ContentExample.inline(
     'silent user @-mention, class order reversed',
     "@_**Greg Price**", // (hypothetical server variation)
     expectedText: 'Greg Price',
     '<p><span class="silent user-mention" data-user-id="2187">Greg Price</span></p>',
-    const UserMentionNode(nodes: [TextNode('Greg Price')], userId: 2187, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('Greg Price')], isSilent: true, userId: 2187));
 
   static final groupMentionPlain = ContentExample.inline(
     'plain group @-mention',
     "@*test-empty*",
     expectedText: '@test-empty',
     '<p><span class="user-group-mention" data-user-group-id="186">@test-empty</span></p>',
-    const UserMentionNode(nodes: [TextNode('@test-empty')], userId: null, isSilent: false));
+    const UserGroupMentionNode(nodes: [TextNode('@test-empty')], isSilent: false, userGroupId: 186));
 
   static final groupMentionSilent = ContentExample.inline(
     'silent group @-mention',
     "@_*test-empty*",
     expectedText: 'test-empty',
     '<p><span class="user-group-mention silent" data-user-group-id="186">test-empty</span></p>',
-    const UserMentionNode(nodes: [TextNode('test-empty')], userId: null, isSilent: true));
+    const UserGroupMentionNode(nodes: [TextNode('test-empty')], isSilent: true, userGroupId: 186));
 
   static final groupMentionSilentClassOrderReversed = ContentExample.inline(
     'silent group @-mention, class order reversed',
     "@_*test-empty*", // (hypothetical server variation)
     expectedText: 'test-empty',
     '<p><span class="silent user-group-mention" data-user-group-id="186">test-empty</span></p>',
-    const UserMentionNode(nodes: [TextNode('test-empty')], userId: null, isSilent: true));
+    const UserGroupMentionNode(nodes: [TextNode('test-empty')], isSilent: true, userGroupId: 186));
 
   static final channelWildcardMentionPlain = ContentExample.inline(
     'plain channel wildcard @-mention',
     "@**all**",
     expectedText: '@all',
     '<p><span class="user-mention channel-wildcard-mention" data-user-id="*">@all</span></p>',
-    const UserMentionNode(nodes: [TextNode('@all')], userId: null, isSilent: false));
+    const UserMentionNode(nodes: [TextNode('@all')], isSilent: false, userId: null));
 
   static final channelWildcardMentionSilent = ContentExample.inline(
     'silent channel wildcard @-mention',
     "@_**everyone**",
     expectedText: 'everyone',
     '<p><span class="user-mention channel-wildcard-mention silent" data-user-id="*">everyone</span></p>',
-    const UserMentionNode(nodes: [TextNode('everyone')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('everyone')], isSilent: true, userId: null));
 
   static final channelWildcardMentionSilentClassOrderReversed = ContentExample.inline(
     'silent channel wildcard @-mention, class order reversed',
     "@_**channel**", // (hypothetical server variation)
     expectedText: 'channel',
     '<p><span class="silent user-mention channel-wildcard-mention" data-user-id="*">channel</span></p>',
-    const UserMentionNode(nodes: [TextNode('channel')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('channel')], isSilent: true, userId: null));
 
   static final legacyChannelWildcardMentionPlain = ContentExample.inline(
     'legacy plain channel wildcard @-mention',
     "@**channel**",
     expectedText: '@channel',
     '<p><span class="user-mention" data-user-id="*">@channel</span></p>',
-    const UserMentionNode(nodes: [TextNode('@channel')], userId: null, isSilent: false));
+    const UserMentionNode(nodes: [TextNode('@channel')], isSilent: false, userId: null));
 
   static final legacyChannelWildcardMentionSilent = ContentExample.inline(
     'legacy silent channel wildcard @-mention',
     "@_**stream**",
     expectedText: 'stream',
     '<p><span class="user-mention silent" data-user-id="*">stream</span></p>',
-    const UserMentionNode(nodes: [TextNode('stream')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('stream')], isSilent: true, userId: null));
 
   static final legacyChannelWildcardMentionSilentClassOrderReversed = ContentExample.inline(
     'legacy silent channel wildcard @-mention, class order reversed',
     "@_**all**", // (hypothetical server variation)
     expectedText: 'all',
     '<p><span class="silent user-mention" data-user-id="*">all</span></p>',
-    const UserMentionNode(nodes: [TextNode('all')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('all')], isSilent: true, userId: null));
 
   static final topicMentionPlain = ContentExample.inline(
     'plain @-topic',
     "@**topic**",
     expectedText: '@topic',
     '<p><span class="topic-mention">@topic</span></p>',
-    const UserMentionNode(nodes: [TextNode('@topic')], userId: null, isSilent: false));
+    const UserMentionNode(nodes: [TextNode('@topic')], isSilent: false, userId: null));
 
   static final topicMentionSilent = ContentExample.inline(
     'silent @-topic',
     "@_**topic**",
     expectedText: 'topic',
     '<p><span class="topic-mention silent">topic</span></p>',
-    const UserMentionNode(nodes: [TextNode('topic')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('topic')], isSilent: true, userId: null));
 
   static final topicMentionSilentClassOrderReversed = ContentExample.inline(
     'silent @-topic, class order reversed',
     "@_**topic**", // (hypothetical server variation)
     expectedText: 'topic',
     '<p><span class="silent topic-mention">topic</span></p>',
-    const UserMentionNode(nodes: [TextNode('topic')], userId: null, isSilent: true));
+    const UserMentionNode(nodes: [TextNode('topic')], isSilent: true, userId: null));
 
   static final emojiUnicode = ContentExample.inline(
     'Unicode emoji, encoded in span element',
diff --git a/test/widgets/action_sheet_test.dart b/test/widgets/action_sheet_test.dart
index 45bd24ca90..17af6893eb 100644
--- a/test/widgets/action_sheet_test.dart
+++ b/test/widgets/action_sheet_test.dart
@@ -1429,7 +1429,7 @@ void main() {
         checkSenderAndTimestampShown(tester, senderId: message.senderId);
         check(find.descendant(
           of: find.byType(BottomSheet),
-          matching: find.byType(UserMention))
+          matching: find.byType(Mention))
         ).findsOne();
       });
 
@@ -1452,7 +1452,7 @@ void main() {
         checkSenderAndTimestampShown(tester, senderId: message.senderId);
         check(find.descendant(
           of: find.byType(BottomSheet),
-          matching: find.byType(UserMention))
+          matching: find.byType(Mention))
         ).findsOne();
       });
 
diff --git a/test/widgets/content_test.dart b/test/widgets/content_test.dart
index ab68e97d7a..195c9c8661 100644
--- a/test/widgets/content_test.dart
+++ b/test/widgets/content_test.dart
@@ -980,7 +980,7 @@ void main() {
     });
   });
 
-  group('UserMention', () {
+  group('Mention', () {
     testContentSmoke(ContentExample.userMentionPlain,
       wrapWithPerAccountStoreWidget: true);
     testContentSmoke(ContentExample.userMentionSilent,
@@ -1008,10 +1008,10 @@ void main() {
     testContentSmoke(ContentExample.topicMentionSilentClassOrderReversed,
       wrapWithPerAccountStoreWidget: true);
 
-    UserMention? findUserMentionInSpan(InlineSpan rootSpan) {
-      UserMention? result;
+    Mention? findMentionInSpan(InlineSpan rootSpan) {
+      Mention? result;
       rootSpan.visitChildren((span) {
-        if (span case (WidgetSpan(child: UserMention() && var widget))) {
+        if (span case (WidgetSpan(child: Mention() && var widget))) {
           result = widget;
           return false;
         }
@@ -1020,7 +1020,7 @@ void main() {
       return result;
     }
 
-    TextStyle textStyleFromWidget(WidgetTester tester, UserMention widget, String mentionText) {
+    TextStyle textStyleFromWidget(WidgetTester tester, Mention widget, String mentionText) {
       return mergedStyleOf(tester,
         findAncestor: find.byWidget(widget), mentionText)!;
     }
@@ -1030,7 +1030,7 @@ void main() {
         targetHtml: '<span class="user-mention" data-user-id="13313">@Chris Bobbe</span>',
         wrapWithPerAccountStoreWidget: true,
         targetFontSizeFinder: (rootSpan) {
-          final widget = findUserMentionInSpan(rootSpan);
+          final widget = findMentionInSpan(rootSpan);
           final style = textStyleFromWidget(tester, widget!, '@Chris Bobbe');
           return style.fontSize!;
         });
@@ -1044,7 +1044,7 @@ void main() {
       wrapWithPerAccountStoreWidget: true,
       styleFinder: (tester) {
         return textStyleFromWidget(tester,
-          tester.widget(find.byType(UserMention)), 'Greg Price');
+          tester.widget(find.byType(Mention)), 'Greg Price');
       });
 
     // TODO(#647):
@@ -1059,14 +1059,14 @@ void main() {
       wrapWithPerAccountStoreWidget: true,
       styleFinder: (tester) {
         return textStyleFromWidget(tester,
-          tester.widget(find.byType(UserMention)), 'Chris Bobbe');
+          tester.widget(find.byType(Mention)), 'Chris Bobbe');
       });
 
     // TODO(#647):
     //  testFontWeight('non-silent self-user mention in bold context',
     //    expectedWght: 800, // [etc.]
 
-    group('dynamic name resolution', () {
+    group('user mention dynamic name resolution', () {
       Future<void> prepare({
         required WidgetTester tester,
         required String html,
@@ -1111,6 +1111,45 @@ void main() {
         check(find.text('@New Name')).findsNothing();
       });
     });
+
+    group('user group mention dynamic name resolution', () {
+      Future<void> prepare({
+        required WidgetTester tester,
+        required String html,
+        List<UserGroup>? userGroups,
+      }) async {
+        final initialSnapshot = eg.initialSnapshot(realmUserGroups: userGroups);
+        await prepareContent(tester,
+          wrapWithPerAccountStoreWidget: true,
+          initialSnapshot: initialSnapshot,
+          plainContent(html));
+      }
+
+      testWidgets('resolves current user group name from store', (tester) async {
+        await prepare(
+          tester: tester,
+          html: '<p><span class="user-group-mention" data-user-group-id="186">@old-name</span></p>',
+          userGroups: [eg.userGroup(id: 186, name: 'new-name')]);
+        check(find.text('@new-name')).findsOne();
+        check(find.text('@old-name')).findsNothing();
+      });
+
+      testWidgets('falls back to original text when user group not found', (tester) async {
+        await prepare(
+          tester: tester,
+          html: '<p><span class="user-group-mention" data-user-group-id="999">@Unknown Group</span></p>');
+        check(find.text('@Unknown Group')).findsOne();
+      });
+
+      testWidgets('handles silent mentions correctly', (tester) async {
+        await prepare(
+          tester: tester,
+          html: '<p><span class="user-group-mention silent" data-user-group-id="186">old-name</span></p>',
+          userGroups: [eg.userGroup(id: 186, name: 'new-name')]);
+        check(find.text('new-name')).findsOne();
+        check(find.text('@new-name')).findsNothing();
+      });
+    });
   });
 
   Future<void> tapText(WidgetTester tester, Finder textFinder) async {