diff --git a/app/controllers/admin/topics_controller.rb b/app/controllers/admin/topics_controller.rb
index c3b1c6793adb65618efcb21097664477b635f3e4..e97ead12f717964e9bc44de519fe3cf098d99a2c 100644
--- a/app/controllers/admin/topics_controller.rb
+++ b/app/controllers/admin/topics_controller.rb
@@ -49,11 +49,8 @@ def merge
     source_topic = Projects::Topic.find(merge_params[:source_topic_id])
     target_topic = Projects::Topic.find(merge_params[:target_topic_id])
 
-    begin
-      ::Topics::MergeService.new(source_topic, target_topic).execute
-    rescue ArgumentError => e
-      return render status: :bad_request, json: { type: :alert, message: e.message }
-    end
+    response = ::Topics::MergeService.new(source_topic, target_topic).execute
+    return render status: :bad_request, json: { type: :alert, message: response.message } if response.error?
 
     message = _('Topic %{source_topic} was successfully merged into topic %{target_topic}.')
     flash[:toast] = message % { source_topic: source_topic.name, target_topic: target_topic.name }
diff --git a/app/services/topics/merge_service.rb b/app/services/topics/merge_service.rb
index 0d256579fe04d7e2396c890e74cf155eed90b857..58f3d5305b48efbcbc911fff7cd1af356488b453 100644
--- a/app/services/topics/merge_service.rb
+++ b/app/services/topics/merge_service.rb
@@ -17,14 +17,21 @@ def execute
         refresh_target_topic_counters
         delete_source_topic
       end
+
+      ServiceResponse.success
+    rescue ArgumentError => e
+      ServiceResponse.error(message: e.message)
+    rescue StandardError => e
+      Gitlab::ErrorTracking.track_exception(e, source_topic_id: source_topic.id, target_topic_id: target_topic.id)
+      ServiceResponse.error(message: _('Topics could not be merged!'))
     end
 
     private
 
     def validate_parameters!
-      raise ArgumentError, 'The source topic is not a topic.' unless source_topic.is_a?(Projects::Topic)
-      raise ArgumentError, 'The target topic is not a topic.' unless target_topic.is_a?(Projects::Topic)
-      raise ArgumentError, 'The source topic and the target topic are identical.' if source_topic == target_topic
+      raise ArgumentError, _('The source topic is not a topic.') unless source_topic.is_a?(Projects::Topic)
+      raise ArgumentError, _('The target topic is not a topic.') unless target_topic.is_a?(Projects::Topic)
+      raise ArgumentError, _('The source topic and the target topic are identical.') if source_topic == target_topic
     end
 
     # rubocop: disable CodeReuse/ActiveRecord
diff --git a/doc/api/topics.md b/doc/api/topics.md
index ee88a43ff1c412eb13488b070862e08025c40f13..38d99244bb6ef04d28170a01a2f057f633c71c54 100644
--- a/doc/api/topics.md
+++ b/doc/api/topics.md
@@ -217,7 +217,7 @@ curl --request PUT \
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80725) in GitLab 14.9.
 
-You must be an administrator to delete a project.
+You must be an administrator to delete a project topic.
 When you delete a project topic, you also delete the topic assignment for projects.
 
 ```plaintext
@@ -237,3 +237,43 @@ curl --request DELETE \
      --header "PRIVATE-TOKEN: <your_access_token>" \
      "https://gitlab.example.com/api/v4/topics/1"
 ```
+
+## Merge topics
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/95501) in GitLab 15.4.
+
+You must be an administrator to merge a source topic into a target topic.
+When you merge topics, you delete the source topic and move all assigned projects to the target topic.
+
+```plaintext
+POST /topics/merge
+```
+
+Supported attributes:
+
+| Attribute         | Type    | Required               | Description                |
+| ----------------- | ------- | ---------------------- | -------------------------- |
+| `source_topic_id` | integer | **{check-circle}** Yes | ID of source project topic |
+| `target_topic_id` | integer | **{check-circle}** Yes | ID of target project topic |
+
+Example request:
+
+```shell
+curl --request POST \
+     --data "source_topic_id=2&target_topic_id=1" \
+     --header "PRIVATE-TOKEN: <your_access_token>" \
+     "https://gitlab.example.com/api/v4/topics/merge"
+```
+
+Example response:
+
+```json
+{
+  "id": 1,
+  "name": "topic1",
+  "title": "Topic 1",
+  "description": null,
+  "total_projects_count": 0,
+  "avatar_url": null
+}
+```
diff --git a/lib/api/topics.rb b/lib/api/topics.rb
index a08b4c6c1070e7eb16816749a6ab9f8a6ba53040..38cfdc44021adcf9abf9b551fd775c06a0c510d7 100644
--- a/lib/api/topics.rb
+++ b/lib/api/topics.rb
@@ -94,5 +94,25 @@ class Topics < ::API::Base
 
       destroy_conditionally!(topic)
     end
+
+    desc 'Merge topics' do
+      detail 'This feature was introduced in GitLab 15.4.'
+      success Entities::Projects::Topic
+    end
+    params do
+      requires :source_topic_id, type: Integer, desc: 'ID of source project topic'
+      requires :target_topic_id, type: Integer, desc: 'ID of target project topic'
+    end
+    post 'topics/merge' do
+      authenticated_as_admin!
+
+      source_topic = ::Projects::Topic.find(params[:source_topic_id])
+      target_topic = ::Projects::Topic.find(params[:target_topic_id])
+
+      response = ::Topics::MergeService.new(source_topic, target_topic).execute
+      render_api_error!(response.message, :bad_request) if response.error?
+
+      present target_topic, with: Entities::Projects::Topic
+    end
   end
 end
diff --git a/locale/gitlab.pot b/locale/gitlab.pot
index bcfc87fa07845f680c203cad5c704ec9dac0e86c..9d33cbedb36c731507fb0d99edf15c1b028b7496 100644
--- a/locale/gitlab.pot
+++ b/locale/gitlab.pot
@@ -39553,6 +39553,12 @@ msgstr ""
 msgid "The source project of this merge request has been removed."
 msgstr ""
 
+msgid "The source topic and the target topic are identical."
+msgstr ""
+
+msgid "The source topic is not a topic."
+msgstr ""
+
 msgid "The specified tab is invalid, please select another"
 msgstr ""
 
@@ -39565,6 +39571,9 @@ msgstr ""
 msgid "The tag name can't be changed for an existing release."
 msgstr ""
 
+msgid "The target topic is not a topic."
+msgstr ""
+
 msgid "The time period in seconds that the maximum requests per project limit applies to."
 msgstr ""
 
@@ -41270,6 +41279,9 @@ msgstr ""
 msgid "Topics"
 msgstr ""
 
+msgid "Topics could not be merged!"
+msgstr ""
+
 msgid "Total"
 msgstr ""
 
diff --git a/spec/controllers/admin/topics_controller_spec.rb b/spec/controllers/admin/topics_controller_spec.rb
index 87093e0263bbbfafe870f93d9884e3b38e32e6e1..111fdcc3be6c470679686a19cf3a409dfbc74d5c 100644
--- a/spec/controllers/admin/topics_controller_spec.rb
+++ b/spec/controllers/admin/topics_controller_spec.rb
@@ -194,7 +194,7 @@
     end
 
     it 'renders a 400 error for identical topic ids' do
-      post :merge, params: { source_topic_id: topic, target_topic_id: topic.id }
+      post :merge, params: { source_topic_id: topic.id, target_topic_id: topic.id }
 
       expect(response).to have_gitlab_http_status(:bad_request)
       expect { topic.reload }.not_to raise_error
diff --git a/spec/requests/api/topics_spec.rb b/spec/requests/api/topics_spec.rb
index 72221e3fb6a8156e71e7e278169fd7850645efaa..1ad6f876fabdfdc6e81d7bd5ea1a79da5ffec7fd 100644
--- a/spec/requests/api/topics_spec.rb
+++ b/spec/requests/api/topics_spec.rb
@@ -317,4 +317,66 @@
       end
     end
   end
+
+  describe 'POST /topics/merge', :aggregate_failures do
+    context 'as administrator' do
+      let_it_be(:api_url) { api('/topics/merge', admin) }
+
+      it 'merge topics' do
+        post api_url, params: { source_topic_id: topic_3.id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:created)
+        expect { topic_2.reload }.not_to raise_error
+        expect { topic_3.reload }.to raise_error(ActiveRecord::RecordNotFound)
+        expect(json_response['id']).to eq(topic_2.id)
+        expect(json_response['total_projects_count']).to eq(topic_2.total_projects_count)
+      end
+
+      it 'returns 404 for non existing source topic id' do
+        post api_url, params: { source_topic_id: non_existing_record_id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+
+      it 'returns 404 for non existing target topic id' do
+        post api_url, params: { source_topic_id: topic_3.id, target_topic_id: non_existing_record_id }
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+
+      it 'returns 400 for identical topic ids' do
+        post api_url, params: { source_topic_id: topic_2.id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:bad_request)
+        expect(json_response['message']).to eql('The source topic and the target topic are identical.')
+      end
+
+      it 'returns 400 if merge failed' do
+        allow_next_found_instance_of(Projects::Topic) do |topic|
+          allow(topic).to receive(:destroy!).and_raise(ActiveRecord::RecordNotDestroyed)
+        end
+
+        post api_url, params: { source_topic_id: topic_3.id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:bad_request)
+        expect(json_response['message']).to eql('Topics could not be merged!')
+      end
+    end
+
+    context 'as normal user' do
+      it 'returns 403 Forbidden' do
+        post api('/topics/merge', user), params: { source_topic_id: topic_3.id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:forbidden)
+      end
+    end
+
+    context 'as anonymous' do
+      it 'returns 401 Unauthorized' do
+        post api('/topics/merge'), params: { source_topic_id: topic_3.id, target_topic_id: topic_2.id }
+
+        expect(response).to have_gitlab_http_status(:unauthorized)
+      end
+    end
+  end
 end
diff --git a/spec/services/topics/merge_service_spec.rb b/spec/services/topics/merge_service_spec.rb
index 971917eb8e9bd4a5ab2bb543eaf519196718697b..eef31817aa8d42b556fa7e55da1616ac3211ed7c 100644
--- a/spec/services/topics/merge_service_spec.rb
+++ b/spec/services/topics/merge_service_spec.rb
@@ -30,7 +30,9 @@
       it 'reverts previous changes' do
         allow(source_topic.reload).to receive(:destroy!).and_raise(ActiveRecord::RecordNotDestroyed)
 
-        expect { subject }.to raise_error(ActiveRecord::RecordNotDestroyed)
+        response = subject
+        expect(response).to be_error
+        expect(response.message).to eq('Topics could not be merged!')
 
         expect(source_topic.projects).to contain_exactly(project_1, project_2, project_4)
         expect(target_topic.projects).to contain_exactly(project_3, project_4)
@@ -50,9 +52,9 @@
 
       with_them do
         it 'raises correct error' do
-          expect { subject }.to raise_error(ArgumentError) do |error|
-            expect(error.message).to eq(expected_message)
-          end
+          response = subject
+          expect(response).to be_error
+          expect(response.message).to eq(expected_message)
         end
       end
     end