diff --git a/frontend_tests/node_tests/composebox_typeahead.js b/frontend_tests/node_tests/composebox_typeahead.js
index 718dbd4178..d6d6419693 100644
--- a/frontend_tests/node_tests/composebox_typeahead.js
+++ b/frontend_tests/node_tests/composebox_typeahead.js
@@ -291,7 +291,7 @@ const hamletcharacters = {
     description: "Characters of Hamlet",
     members: new Set([100, 104]),
     is_system_group: false,
-    subgroups: new Set([10, 11]),
+    direct_subgroup_ids: new Set([10, 11]),
 };
 
 const backend = {
@@ -300,7 +300,7 @@ const backend = {
     description: "Backend team",
     members: new Set([]),
     is_system_group: false,
-    subgroups: new Set([]),
+    direct_subgroup_ids: new Set([]),
 };
 
 const call_center = {
@@ -309,7 +309,7 @@ const call_center = {
     description: "folks working in support",
     members: new Set([]),
     is_system_group: false,
-    subgroups: new Set([]),
+    direct_subgroup_ids: new Set([]),
 };
 
 const make_emoji = (emoji_dict) => ({
diff --git a/frontend_tests/node_tests/dispatch.js b/frontend_tests/node_tests/dispatch.js
index 0e602208fe..6c97de99ef 100644
--- a/frontend_tests/node_tests/dispatch.js
+++ b/frontend_tests/node_tests/dispatch.js
@@ -184,9 +184,9 @@ run_test("user groups", ({override}) => {
         override(user_groups, "add_subgroups", stub.f);
         dispatch(event);
         assert.equal(stub.num_calls, 1);
-        const args = stub.get_args("group_id", "subgroup_ids");
+        const args = stub.get_args("group_id", "direct_subgroup_ids");
         assert_same(args.group_id, event.group_id);
-        assert_same(args.subgroup_ids, event.subgroup_ids);
+        assert_same(args.direct_subgroup_ids, event.direct_subgroup_ids);
     }
 
     event = event_fixtures.user_group__remove_members;
@@ -206,9 +206,9 @@ run_test("user groups", ({override}) => {
         override(user_groups, "remove_subgroups", stub.f);
         dispatch(event);
         assert.equal(stub.num_calls, 1);
-        const args = stub.get_args("group_id", "subgroup_ids");
+        const args = stub.get_args("group_id", "direct_subgroup_ids");
         assert_same(args.group_id, event.group_id);
-        assert_same(args.subgroup_ids, event.subgroup_ids);
+        assert_same(args.direct_subgroup_ids, event.direct_subgroup_ids);
     }
 
     event = event_fixtures.user_group__update;
diff --git a/frontend_tests/node_tests/lib/events.js b/frontend_tests/node_tests/lib/events.js
index 083cb6a554..e76ff0b656 100644
--- a/frontend_tests/node_tests/lib/events.js
+++ b/frontend_tests/node_tests/lib/events.js
@@ -735,7 +735,7 @@ exports.fixtures = {
             description: "mobile folks",
             members: [1],
             is_system_group: false,
-            subgroups: [2],
+            direct_subgroup_ids: [2],
         },
     },
 
@@ -750,7 +750,7 @@ exports.fixtures = {
         type: "user_group",
         op: "add_subgroups",
         group_id: 1,
-        subgroup_ids: [3],
+        direct_subgroup_ids: [3],
     },
 
     user_group__remove: {
@@ -770,7 +770,7 @@ exports.fixtures = {
         type: "user_group",
         op: "remove_subgroups",
         group_id: 1,
-        subgroup_ids: [3],
+        direct_subgroup_ids: [3],
     },
 
     user_group__update: {
diff --git a/frontend_tests/node_tests/user_groups.js b/frontend_tests/node_tests/user_groups.js
index 26df424310..6af61c33c9 100644
--- a/frontend_tests/node_tests/user_groups.js
+++ b/frontend_tests/node_tests/user_groups.js
@@ -15,7 +15,7 @@ run_test("user_groups", () => {
         id: 0,
         members: new Set([1, 2]),
         is_system_group: false,
-        subgroups: new Set([4, 5]),
+        direct_subgroup_ids: new Set([4, 5]),
     };
 
     const params = {};
@@ -32,14 +32,14 @@ run_test("user_groups", () => {
         id: 1,
         members: new Set([3]),
         is_system_group: false,
-        subgroups: new Set([]),
+        direct_subgroup_ids: new Set([]),
     };
     const all = {
         name: "Everyone",
         id: 2,
         members: new Set([1, 2, 3]),
         is_system_group: false,
-        subgroups: new Set([4, 5, 6]),
+        direct_subgroup_ids: new Set([4, 5, 6]),
     };
 
     user_groups.add(admins);
@@ -101,12 +101,15 @@ run_test("user_groups", () => {
 
     user_groups.add_subgroups(all.id, [2, 3]);
     assert.deepEqual(
-        user_groups.get_user_group_from_id(all.id).subgroups,
+        user_groups.get_user_group_from_id(all.id).direct_subgroup_ids,
         new Set([2, 3, 5, 4, 6]),
     );
 
     user_groups.remove_subgroups(all.id, [2, 4]);
-    assert.deepEqual(user_groups.get_user_group_from_id(all.id).subgroups, new Set([3, 5, 6]));
+    assert.deepEqual(
+        user_groups.get_user_group_from_id(all.id).direct_subgroup_ids,
+        new Set([3, 5, 6]),
+    );
 
     assert.ok(user_groups.is_user_group(admins));
     const object = {
@@ -135,28 +138,28 @@ run_test("get_recursive_subgroups", () => {
         id: 1,
         members: new Set([1]),
         is_system_group: false,
-        subgroups: new Set([4]),
+        direct_subgroup_ids: new Set([4]),
     };
     const all = {
         name: "Everyone",
         id: 2,
         members: new Set([2, 3]),
         is_system_group: false,
-        subgroups: new Set([1, 3]),
+        direct_subgroup_ids: new Set([1, 3]),
     };
     const test = {
         name: "Test",
         id: 3,
         members: new Set([3, 4, 5]),
         is_system_group: false,
-        subgroups: new Set([2]),
+        direct_subgroup_ids: new Set([2]),
     };
     const foo = {
         name: "Foo",
         id: 4,
         members: new Set([6, 7]),
         is_system_group: false,
-        subgroups: new Set([]),
+        direct_subgroup_ids: new Set([]),
     };
 
     user_groups.add(admins);
@@ -190,28 +193,28 @@ run_test("is_user_in_group", () => {
         id: 1,
         members: new Set([1]),
         is_system_group: false,
-        subgroups: new Set([4]),
+        direct_subgroup_ids: new Set([4]),
     };
     const all = {
         name: "Everyone",
         id: 2,
         members: new Set([2, 3]),
         is_system_group: false,
-        subgroups: new Set([1, 3]),
+        direct_subgroup_ids: new Set([1, 3]),
     };
     const test = {
         name: "Test",
         id: 3,
         members: new Set([4, 5]),
         is_system_group: false,
-        subgroups: new Set([1]),
+        direct_subgroup_ids: new Set([1]),
     };
     const foo = {
         name: "Foo",
         id: 4,
         members: new Set([6, 7]),
         is_system_group: false,
-        subgroups: new Set([]),
+        direct_subgroup_ids: new Set([]),
     };
     user_groups.add(admins);
     user_groups.add(all);
diff --git a/static/js/server_events_dispatch.js b/static/js/server_events_dispatch.js
index 4acb6a255e..8bdd81c8a6 100644
--- a/static/js/server_events_dispatch.js
+++ b/static/js/server_events_dispatch.js
@@ -755,10 +755,10 @@ export function dispatch_normal_event(event) {
                     user_groups.remove_members(event.group_id, event.user_ids);
                     break;
                 case "add_subgroups":
-                    user_groups.add_subgroups(event.group_id, event.subgroup_ids);
+                    user_groups.add_subgroups(event.group_id, event.direct_subgroup_ids);
                     break;
                 case "remove_subgroups":
-                    user_groups.remove_subgroups(event.group_id, event.subgroup_ids);
+                    user_groups.remove_subgroups(event.group_id, event.direct_subgroup_ids);
                     break;
                 case "update":
                     user_groups.update(event);
diff --git a/static/js/user_groups.ts b/static/js/user_groups.ts
index 3c6146106f..048e35f1eb 100644
--- a/static/js/user_groups.ts
+++ b/static/js/user_groups.ts
@@ -8,7 +8,7 @@ type UserGroup = {
     name: string;
     members: Set<number>;
     is_system_group: boolean;
-    subgroups: Set<number>;
+    direct_subgroup_ids: Set<number>;
 };
 
 // The members field is a number array which we convert
@@ -36,7 +36,7 @@ export function add(user_group_raw: UserGroupRaw): void {
         name: user_group_raw.name,
         members: new Set(user_group_raw.members),
         is_system_group: user_group_raw.is_system_group,
-        subgroups: new Set(user_group_raw.subgroups),
+        direct_subgroup_ids: new Set(user_group_raw.direct_subgroup_ids),
     };
 
     user_group_name_dict.set(user_group.name, user_group);
@@ -120,7 +120,7 @@ export function add_subgroups(user_group_id: number, subgroup_ids: number[]): vo
     }
 
     for (const subgroup_id of subgroup_ids) {
-        user_group.subgroups.add(subgroup_id);
+        user_group.direct_subgroup_ids.add(subgroup_id);
     }
 }
 
@@ -132,7 +132,7 @@ export function remove_subgroups(user_group_id: number, subgroup_ids: number[]):
     }
 
     for (const subgroup_id of subgroup_ids) {
-        user_group.subgroups.delete(subgroup_id);
+        user_group.direct_subgroup_ids.delete(subgroup_id);
     }
 }
 
@@ -164,7 +164,7 @@ export function get_recursive_subgroups(target_group_id: number): Set<number> |
     // Correctness of this algorithm relying on the ES6 Set
     // implementation having the property that a `for of` loop will
     // visit all items that are added to the set during the loop.
-    const subgroup_ids = new Set(target_user_group.subgroups);
+    const subgroup_ids = new Set(target_user_group.direct_subgroup_ids);
     for (const subgroup_id of subgroup_ids) {
         const subgroup = user_group_by_id_dict.get(subgroup_id);
         if (subgroup === undefined) {
@@ -172,7 +172,7 @@ export function get_recursive_subgroups(target_group_id: number): Set<number> |
             return undefined;
         }
 
-        for (const direct_subgroup_id of subgroup.subgroups) {
+        for (const direct_subgroup_id of subgroup.direct_subgroup_ids) {
             subgroup_ids.add(direct_subgroup_id);
         }
     }
diff --git a/templates/zerver/api/changelog.md b/templates/zerver/api/changelog.md
index a134297360..8bd6ac389c 100644
--- a/templates/zerver/api/changelog.md
+++ b/templates/zerver/api/changelog.md
@@ -20,6 +20,14 @@ format used by the Zulip server that they are interacting with.
 
 ## Changes in Zulip 6.0
 
+**Feature level 131**
+
+* [`GET /user_groups`](/api/get-user-groups),[`POST
+  /register`](/api/register-queue): Renamed `subgroups` field in
+  the user group objects to `direct_subgroup_ids`.
+* [`GET /events`](/api/get-events): Renamed `subgroup_ids` field
+  in the group object to `direct_subgroup_ids`.
+
 **Feature level 130**
 
 * `PATCH /bots/{bot_user_id}`: Added support for changing a bot's role
diff --git a/zerver/actions/user_groups.py b/zerver/actions/user_groups.py
index c417856603..6ea23a06db 100644
--- a/zerver/actions/user_groups.py
+++ b/zerver/actions/user_groups.py
@@ -100,7 +100,7 @@ def do_send_create_user_group_event(
             description=user_group.description,
             id=user_group.id,
             is_system_group=user_group.is_system_group,
-            subgroups=[subgroup.id for subgroup in subgroups],
+            direct_subgroup_ids=[subgroup.id for subgroup in subgroups],
         ),
     )
     send_event(user_group.realm, event, active_user_ids(user_group.realm_id))
@@ -169,7 +169,7 @@ def do_send_subgroups_update_event(
     event_name: str, user_group: UserGroup, subgroup_ids: List[int]
 ) -> None:
     event = dict(
-        type="user_group", op=event_name, group_id=user_group.id, subgroup_ids=subgroup_ids
+        type="user_group", op=event_name, group_id=user_group.id, direct_subgroup_ids=subgroup_ids
     )
     transaction.on_commit(
         lambda: send_event(user_group.realm, event, active_user_ids(user_group.realm_id))
diff --git a/zerver/lib/event_schema.py b/zerver/lib/event_schema.py
index 4ebea066ee..579d51bb9d 100644
--- a/zerver/lib/event_schema.py
+++ b/zerver/lib/event_schema.py
@@ -1676,7 +1676,7 @@ group_type = DictType(
         ("id", int),
         ("name", str),
         ("members", ListType(int)),
-        ("subgroups", ListType(int)),
+        ("direct_subgroup_ids", ListType(int)),
         ("description", str),
         ("is_system_group", bool),
     ]
@@ -1753,7 +1753,7 @@ user_group_add_subgroups_event = event_dict_type(
         ("type", Equals("user_group")),
         ("op", Equals("add_subgroups")),
         ("group_id", int),
-        ("subgroup_ids", ListType(int)),
+        ("direct_subgroup_ids", ListType(int)),
     ]
 )
 check_user_group_add_subgroups = make_checker(user_group_add_subgroups_event)
@@ -1764,7 +1764,7 @@ user_group_remove_subgroups_event = event_dict_type(
         ("type", Equals("user_group")),
         ("op", Equals("remove_subgroups")),
         ("group_id", int),
-        ("subgroup_ids", ListType(int)),
+        ("direct_subgroup_ids", ListType(int)),
     ]
 )
 check_user_group_remove_subgroups = make_checker(user_group_remove_subgroups_event)
diff --git a/zerver/lib/events.py b/zerver/lib/events.py
index 1ee558749e..2afe7c2592 100644
--- a/zerver/lib/events.py
+++ b/zerver/lib/events.py
@@ -1249,14 +1249,16 @@ def apply_event(
         elif event["op"] == "add_subgroups":
             for user_group in state["realm_user_groups"]:
                 if user_group["id"] == event["group_id"]:
-                    user_group["subgroups"].extend(event["subgroup_ids"])
-                    user_group["subgroups"].sort()
+                    user_group["direct_subgroup_ids"].extend(event["direct_subgroup_ids"])
+                    user_group["direct_subgroup_ids"].sort()
         elif event["op"] == "remove_subgroups":
             for user_group in state["realm_user_groups"]:
                 if user_group["id"] == event["group_id"]:
-                    subgroups = set(user_group["subgroups"])
-                    user_group["subgroups"] = list(subgroups - set(event["subgroup_ids"]))
-                    user_group["subgroups"].sort()
+                    subgroups = set(user_group["direct_subgroup_ids"])
+                    user_group["direct_subgroup_ids"] = list(
+                        subgroups - set(event["direct_subgroup_ids"])
+                    )
+                    user_group["direct_subgroup_ids"].sort()
         elif event["op"] == "remove":
             state["realm_user_groups"] = [
                 ug for ug in state["realm_user_groups"] if ug["id"] != event["group_id"]
diff --git a/zerver/lib/user_groups.py b/zerver/lib/user_groups.py
index 1164aa4dd9..7bd2dafdf2 100644
--- a/zerver/lib/user_groups.py
+++ b/zerver/lib/user_groups.py
@@ -62,7 +62,7 @@ def user_groups_in_realm_serialized(realm: Realm) -> List[Dict[str, Any]]:
             name=user_group.name,
             description=user_group.description,
             members=[],
-            subgroups=[],
+            direct_subgroup_ids=[],
             is_system_group=user_group.is_system_group,
         )
 
@@ -76,11 +76,11 @@ def user_groups_in_realm_serialized(realm: Realm) -> List[Dict[str, Any]]:
         "subgroup_id", "supergroup_id"
     )
     for (subgroup_id, supergroup_id) in group_membership:
-        group_dicts[supergroup_id]["subgroups"].append(subgroup_id)
+        group_dicts[supergroup_id]["direct_subgroup_ids"].append(subgroup_id)
 
     for group_dict in group_dicts.values():
         group_dict["members"] = sorted(group_dict["members"])
-        group_dict["subgroups"] = sorted(group_dict["subgroups"])
+        group_dict["direct_subgroup_ids"] = sorted(group_dict["direct_subgroup_ids"])
 
     return sorted(group_dicts.values(), key=lambda group_dict: group_dict["id"])
 
diff --git a/zerver/openapi/zulip.yaml b/zerver/openapi/zulip.yaml
index 7e3906f6c4..037e2efb4e 100644
--- a/zerver/openapi/zulip.yaml
+++ b/zerver/openapi/zulip.yaml
@@ -2853,19 +2853,24 @@ paths:
                                   type: integer
                                   description: |
                                     The ID of the user group whose details have changed.
-                                subgroup_ids:
+                                direct_subgroup_ids:
                                   type: array
                                   items:
                                     type: integer
                                   description: |
                                     Array containing the IDs of the subgroups that have been added
                                     to the user group.
+
+                                    **Changes**: New in Zulip 6.0 (feature level 131).
+                                    Previously, this was called `subgroup_ids`, but
+                                    clients can ignore older events as this feature level
+                                    predates subgroups being fully implemented.
                               example:
                                 {
                                   "type": "user_group",
                                   "op": "add_subgroups",
                                   "group_id": 2,
-                                  "subgroup_ids": [10],
+                                  "direct_subgroup_ids": [10],
                                   "id": 0,
                                 }
                             - type: object
@@ -2891,19 +2896,24 @@ paths:
                                   type: integer
                                   description: |
                                     The ID of the user group whose details have changed.
-                                subgroup_ids:
+                                direct_subgroup_ids:
                                   type: array
                                   items:
                                     type: integer
                                   description: |
                                     Array containing the IDs of the subgroups that have been
                                     removed from the user group.
+
+                                    **Changes**: New in Zulip 6.0 (feature level 131).
+                                    Previously, this was called `subgroup_ids`, but
+                                    clients can ignore older events as this feature level
+                                    predates subgroups being fully implemented.
                               example:
                                 {
                                   "type": "user_group",
                                   "op": "remove_subgroups",
                                   "group_id": 2,
-                                  "subgroup_ids": [10],
+                                  "direct_subgroup_ids": [10],
                                   "id": 0,
                                 }
                             - type: object
@@ -13998,12 +14008,15 @@ paths:
                                 The integer user IDs of the user group members.
                               items:
                                 type: integer
-                            subgroups:
+                            direct_subgroup_ids:
                               type: array
                               description: |
-                                The integer user group IDs of the subgroups.
+                                The integer user group IDs of the direct subgroups.
 
-                                **Changes**: New in Zulip 6.0 (feature level 127).
+                                **Changes**: New in Zulip 6.0 (feature level 131).
+                                Introduced in feature level 127 as `subgroups`, but
+                                clients can ignore older events as this feature level
+                                predates subgroups being fully implemented.
                               items:
                                 type: integer
                             name:
@@ -14031,7 +14044,7 @@ paths:
                               "id": 1,
                               "name": "hamletcharacters",
                               "members": [3, 4],
-                              "subgroups": [],
+                              "direct_subgroup_ids": [],
                               "is_system_group": false,
                             },
                             {
@@ -14039,7 +14052,7 @@ paths:
                               "id": 2,
                               "name": "other users",
                               "members": [1, 2],
-                              "subgroups": [1, 2],
+                              "direct_subgroup_ids": [1, 2],
                               "is_system_group": true,
                             },
                           ],
@@ -14978,15 +14991,18 @@ components:
           description: |
             Array containing the id of the users who are
             members of this user group.
-        subgroups:
+        direct_subgroup_ids:
           type: array
           items:
             type: integer
           description: |
-            Array containing the id of the subgroups of this
-            user group.
+            Array containing the id of the direct_subgroups of
+            this user group.
 
-            **Changes**: New in Zulip 6.0 (feature level 127).
+            **Changes**: New in Zulip 6.0 (feature level 131).
+            Introduced in feature level 127 as `subgroups`, but
+            clients can ignore older events as this feature level
+            predates subgroups being fully implemented.
         id:
           type: integer
           description: |
diff --git a/zerver/tests/test_user_groups.py b/zerver/tests/test_user_groups.py
index b273d9f272..798e088e0e 100644
--- a/zerver/tests/test_user_groups.py
+++ b/zerver/tests/test_user_groups.py
@@ -51,12 +51,12 @@ class UserGroupTestCase(ZulipTestCase):
         self.assertEqual(user_groups[0]["name"], "@role:owners")
         self.assertEqual(user_groups[0]["description"], "Owners of this organization")
         self.assertEqual(set(user_groups[0]["members"]), set(membership))
-        self.assertEqual(user_groups[0]["subgroups"], [])
+        self.assertEqual(user_groups[0]["direct_subgroup_ids"], [])
 
         admins_system_group = UserGroup.objects.get(name="@role:administrators", realm=realm)
         self.assertEqual(user_groups[1]["id"], admins_system_group.id)
-        # Check that owners system group is present in "subgroups"
-        self.assertEqual(user_groups[1]["subgroups"], [user_group.id])
+        # Check that owners system group is present in "direct_subgroup_ids"
+        self.assertEqual(user_groups[1]["direct_subgroup_ids"], [user_group.id])
 
         self.assertEqual(user_groups[8]["id"], empty_user_group.id)
         self.assertEqual(user_groups[8]["name"], "newgroup")