diff --git a/‎docs/gl_objects/milestones.rst‎
Lines changed: 4 additions & 0 deletions b/‎docs/gl_objects/milestones.rst‎
Lines changed: 4 additions & 0 deletions
diff --git a/‎gitlab/v4/objects/milestones.py‎
Lines changed: 3 additions & 2 deletions b/‎gitlab/v4/objects/milestones.py‎
Lines changed: 3 additions & 2 deletions
diff --git a/‎tests/functional/api/test_projects.py‎
Lines changed: 21 additions & 0 deletions b/‎tests/functional/api/test_projects.py‎
Lines changed: 21 additions & 0 deletions
@@ -66,6 +66,10 @@ Change the state of a milestone (activate / close)::
     milestone.state_event = 'activate'
     milestone.save()
 
+Promote a project milestone::
+
+    milestone.promote()
+
 List the issues related to a milestone::
 
     issues = milestone.issues()
 
@@ -2,7 +2,7 @@
 from gitlab import exceptions as exc
 from gitlab import types
 from gitlab.base import RequiredOptional, RESTManager, RESTObject, RESTObjectList
-from gitlab.mixins import CRUDMixin, ObjectDeleteMixin, SaveMixin
+from gitlab.mixins import CRUDMixin, ObjectDeleteMixin, PromoteMixin, SaveMixin
 
 from .issues import GroupIssue, GroupIssueManager, ProjectIssue, ProjectIssueManager
 from .merge_requests import (
@@ -90,8 +90,9 @@ class GroupMilestoneManager(CRUDMixin, RESTManager):
     _types = {"iids": types.ListAttribute}
 
 
-class ProjectMilestone(SaveMixin, ObjectDeleteMixin, RESTObject):
+class ProjectMilestone(PromoteMixin, SaveMixin, ObjectDeleteMixin, RESTObject):
     _short_print_attr = "title"
+    _update_uses_post = True
 
     @cli.register_custom_action("ProjectMilestone")
     @exc.on_http_error(exc.GitlabListError)
 
@@ -199,6 +199,27 @@ def test_project_milestones(project):
     assert len(milestone.merge_requests()) == 0
 
 
+def test_project_milestone_promotion(gl, group):
+    """
+    Milestone promotion requires the project to be a child of a group (not in a user namespace)
+
+    """
+    _id = uuid.uuid4().hex
+    data = {
+        "name": f"test-project-{_id}",
+        "namespace_id": group.id,
+    }
+    project = gl.projects.create(data)
+
+    milestone_title = "promoteme"
+    promoted_milestone = project.milestones.create({"title": milestone_title})
+    promoted_milestone.promote()
+
+    assert any(
+        milestone.title == milestone_title for milestone in group.milestones.list()
+    )
+
+
 def test_project_pages_domains(gl, project):
     domain = project.pagesdomains.create({"domain": "foo.domain.com"})
     assert len(project.pagesdomains.list()) == 1