diff --git a/CHANGELOG.unreleased.md b/CHANGELOG.unreleased.md
index 38919ba49..26e734d18 100644
--- a/CHANGELOG.unreleased.md
+++ b/CHANGELOG.unreleased.md
@@ -8,6 +8,7 @@
 > Users must be able to say: “Nice enhancement, I'm eager to test it”
 
 - [REST API] Add `/groups` collection [Forum#70500](https://xcp-ng.org/forum/post/70500)
+- [REST API] Add `/groups/:id/users` and `/users/:id/groups` collection [Forum#70500](https://xcp-ng.org/forum/post/70500)
 
 ### Bug fixes
 
diff --git a/packages/xo-server/src/xo-mixins/rest-api.mjs b/packages/xo-server/src/xo-mixins/rest-api.mjs
index dbd285b3f..6d4c17f4f 100644
--- a/packages/xo-server/src/xo-mixins/rest-api.mjs
+++ b/packages/xo-server/src/xo-mixins/rest-api.mjs
@@ -326,6 +326,21 @@ export default class RestApi {
       async getObjects(filter, limit) {
         return handleArray(await app.getAllGroups(), filter, limit)
       },
+      routes: {
+        async users(req, res) {
+          const { filter, limit } = req.query
+          await sendObjects(
+            handleArray(
+              await Promise.all(req.object.users.map(id => app.getUser(id).then(getUserPublicProperties))),
+              handleOptionalUserFilter(filter),
+              ifDef(limit, Number)
+            ),
+            req,
+            res,
+            '/users'
+          )
+        },
+      },
     }
     collections.restore = {}
     collections.tasks = {}
@@ -336,6 +351,21 @@ export default class RestApi {
       async getObjects(filter, limit) {
         return handleArray(await app.getAllUsers(), filter, limit)
       },
+      routes: {
+        async groups(req, res) {
+          const { filter, limit } = req.query
+          await sendObjects(
+            handleArray(
+              await Promise.all(req.object.groups.map(id => app.getGroup(id))),
+              handleOptionalUserFilter(filter),
+              ifDef(limit, Number)
+            ),
+            req,
+            res,
+            '/groups'
+          )
+        },
+      },
     }
 
     // normalize collections