diff --git a/ee/app/models/merge_train.rb b/ee/app/models/merge_train.rb
index dfa6105f3a7e74170de9dfacef12c59d06892a30..9891ff51fb0a0823cd8ff8678f6980126428489e 100644
--- a/ee/app/models/merge_train.rb
+++ b/ee/app/models/merge_train.rb
@@ -5,6 +5,8 @@ class MergeTrain < ApplicationRecord
   belongs_to :user
   belongs_to :pipeline, class_name: 'Ci::Pipeline'
 
+  delegate :project, to: :merge_request
+
   class << self
     def all_in_train(merge_request)
       joined_merge_requests(merge_request).order('merge_trains.id ASC')
@@ -25,6 +27,10 @@ def all_next
     self.class.all_in_train(merge_request).where('merge_trains.id > ?', id)
   end
 
+  def index
+    self.class.all_in_train(merge_request).where('merge_trains.id < ?', id).count
+  end
+
   def first_in_train?
     !follower_in_train?
   end
diff --git a/ee/app/serializers/ee/merge_request_widget_entity.rb b/ee/app/serializers/ee/merge_request_widget_entity.rb
index b872aa7b9d301366d7c5877efa970bc7c903e1f8..e595ad178762b3be15ee567d5c1f777e6d5434ff 100644
--- a/ee/app/serializers/ee/merge_request_widget_entity.rb
+++ b/ee/app/serializers/ee/merge_request_widget_entity.rb
@@ -135,10 +135,12 @@ module MergeRequestWidgetEntity
         merge_request.target_project.merge_pipelines_enabled?
       end
 
-      expose :merge_trains_enabled?, as: :merge_trains_enabled do |merge_request|
-        merge_request.target_project.merge_trains_enabled?
+      expose :merge_trains_summary, using: ::MergeTrainsSummaryEntity, if: -> (*) { merge_trains_enabled? } do |merge_request|
+        merge_request
       end
 
+      expose :merge_train, if: -> (merge_request) { merge_request.on_train? }, using: ::MergeTrainEntity
+
       expose :can_push_to_source_branch do |merge_request|
         presenter(merge_request).can_push_to_source_branch?
       end
@@ -176,5 +178,9 @@ def base_pipeline_downloadable_path_for_report_type(file_type)
       object.base_pipeline&.present(current_user: current_user)
         &.downloadable_path_for_report_type(file_type)
     end
+
+    def merge_trains_enabled?
+      object.target_project.merge_trains_enabled?
+    end
   end
 end
diff --git a/ee/app/serializers/merge_train_entity.rb b/ee/app/serializers/merge_train_entity.rb
new file mode 100644
index 0000000000000000000000000000000000000000..b6f9d82d82a52b4adbca60b3b3edc84019b3891a
--- /dev/null
+++ b/ee/app/serializers/merge_train_entity.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class MergeTrainEntity < Grape::Entity
+  include RequestAwareEntity
+
+  expose :index
+  expose :user, using: UserEntity
+  expose :pipeline, using: PipelineEntity
+  expose :created_at
+
+  expose :cancel_path do |merge_train|
+    cancel_train_project_merge_request_path(merge_train.project, merge_train.merge_request)
+  end
+end
diff --git a/ee/app/serializers/merge_trains_summary_entity.rb b/ee/app/serializers/merge_trains_summary_entity.rb
new file mode 100644
index 0000000000000000000000000000000000000000..28e4015ab786c158f359c7ad0abf9fc4bcc94f50
--- /dev/null
+++ b/ee/app/serializers/merge_trains_summary_entity.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class MergeTrainsSummaryEntity < Grape::Entity
+  include RequestAwareEntity
+
+  expose :total_count do |merge_request|
+    MergeTrain.all_in_train(merge_request).count
+  end
+
+  expose :create_path do |merge_request|
+    create_train_project_merge_request_path(merge_request.project, merge_request)
+  end
+end
diff --git a/ee/changelogs/unreleased/expose-merge-train-info.yml b/ee/changelogs/unreleased/expose-merge-train-info.yml
new file mode 100644
index 0000000000000000000000000000000000000000..ca508ce280169de94d28d024f6e28cc4f6d5b0a1
--- /dev/null
+++ b/ee/changelogs/unreleased/expose-merge-train-info.yml
@@ -0,0 +1,5 @@
+---
+title: Expose merge train information
+merge_request: 12966
+author:
+type: added
diff --git a/ee/lib/api/merge_trains.rb b/ee/lib/api/merge_trains.rb
new file mode 100644
index 0000000000000000000000000000000000000000..02a159bad12936f5c52d4ee06a13366d4315f5b2
--- /dev/null
+++ b/ee/lib/api/merge_trains.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module API
+  class MergeTrains < ::Grape::API
+    before { authenticate! }
+
+    helpers do
+      def merge_request
+        @merge_request ||= find_merge_request_with_access(params[:merge_request_iid])
+      end
+    end
+
+    params do
+      requires :id, type: String, desc: 'The ID of a project'
+      requires :merge_request_iid, type: Integer, desc: 'The IID of a merge request'
+    end
+    resource :projects, requirements: ::API::API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
+      segment ':id/merge_requests/:merge_request_iid/trains' do
+        desc 'Get all entries on the merge train' do
+          success ::EE::API::Entities::MergeTrain
+        end
+        get do
+          merge_request = find_merge_request_with_access(params[:merge_request_iid])
+
+          present MergeTrain.all_in_train(merge_request), with: ::EE::API::Entities::MergeTrain
+        end
+
+        desc 'Enqueue a merge request to a train' do
+          success ::EE::API::Entities::MergeTrain
+        end
+        post 'enqueue' do
+          begin
+            merge_request.get_on_train!(current_user)
+
+            present merge_request.merge_train, with: ::EE::API::Entities::MergeTrain, status: :ok
+          rescue => e
+            present { message: e.full_messages }, status: :bad_request
+          end
+      end
+
+      segment ':id/merge_requests/:merge_request_iid/train' do
+        desc 'Get the detail of the merge train' do
+          success ::EE::API::Entities::MergeTrain
+        end
+        get do
+          merge_request = find_merge_request_with_access(params[:merge_request_iid])
+
+          present merge_request.merge_train, with: ::EE::API::Entities::MergeTrain, status: :ok
+        end
+
+        desc 'Dequeue a merge request from a train' do
+          success ::EE::API::Entities::MergeTrain
+        end
+        post 'dequeue' do
+          begin
+            merge_request.get_off_train!
+
+            present merge_request.merge_train, with: ::EE::API::Entities::MergeTrain, status: :ok
+          rescue => e
+            present { message: e.full_messages }, status: :bad_request
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/ee/lib/ee/api/endpoints.rb b/ee/lib/ee/api/endpoints.rb
index f5efdabd89bcfc7252a694bb0ddce67f05e41df2..e81bd9c79487685843b2e3861a94bdeb381007a1 100644
--- a/ee/lib/ee/api/endpoints.rb
+++ b/ee/lib/ee/api/endpoints.rb
@@ -30,6 +30,7 @@ module Endpoints
         mount ::API::ManagedLicenses
         mount ::API::ProjectApprovals
         mount ::API::Vulnerabilities
+        mount ::API::MergeTrains
 
         version 'v3', using: :path do
           # Although the following endpoints are kept behind V3 namespace,
diff --git a/ee/lib/ee/api/entities.rb b/ee/lib/ee/api/entities.rb
index 3273f8fbc04107be19f674f3450077665fca2271..532c89e4447594a90432621305ebea7ec4d56a11 100644
--- a/ee/lib/ee/api/entities.rb
+++ b/ee/lib/ee/api/entities.rb
@@ -445,6 +445,27 @@ class ApprovalState < Grape::Entity
         end
       end
 
+      class MergeTrainsSummary < Grape::Entity
+        expose :total_count do |merge_request|
+          MergeTrain.all_in_train(merge_request).count
+        end
+
+        expose :create_path do |merge_request|
+          create_train_project_merge_request_path(merge_request.project, merge_request)
+        end
+      end
+
+      class MergeTrain < Grape::Entity
+        expose :index
+        expose :user, using: UserEntity
+        expose :pipeline, using: PipelineEntity
+        expose :created_at
+
+        expose :cancel_path do |merge_train|
+          cancel_train_project_merge_request_path(merge_train.project, merge_train.merge_request)
+        end
+      end
+
       class LdapGroup < Grape::Entity
         expose :cn
       end
diff --git a/ee/spec/models/merge_train_spec.rb b/ee/spec/models/merge_train_spec.rb
index 7f2fc3451af3ffeb2a5b5b16013413fe3fe3aad2..66b1aecda2a2e497ad642c858d7ebe3ce67aad72 100644
--- a/ee/spec/models/merge_train_spec.rb
+++ b/ee/spec/models/merge_train_spec.rb
@@ -114,6 +114,22 @@
     end
   end
 
+  describe '#index' do
+    subject { merge_train.index }
+
+    let(:merge_train) { merge_request.merge_train }
+    let!(:merge_request) { create_merge_request_on_train }
+
+    it { is_expected.to eq(0) }
+
+    context 'when the merge train is at the second queue' do
+      let(:merge_train) { merge_request_2.merge_train }
+      let!(:merge_request_2) { create_merge_request_on_train(source_branch: 'improve/awesome') }
+
+      it { is_expected.to eq(1) }
+    end
+  end
+
   def create_merge_request_on_train(target_project: project, target_branch: 'master', source_project: project, source_branch: 'feature')
     create(:merge_request,
       :on_train,
diff --git a/ee/spec/serializers/merge_request_widget_entity_spec.rb b/ee/spec/serializers/merge_request_widget_entity_spec.rb
index aa2c2da1536c8f4347d80d53a9c0321bbbf1c5cc..24354c956dd5f73710ece2f0b08f173279ace177 100644
--- a/ee/spec/serializers/merge_request_widget_entity_spec.rb
+++ b/ee/spec/serializers/merge_request_widget_entity_spec.rb
@@ -195,7 +195,42 @@
     expect(subject.as_json).to include(:pipeline_id)
   end
 
-  it 'has merge trains flag' do
-    expect(subject.as_json).to include(:merge_trains_enabled)
+  describe 'Merge Trains' do
+    let!(:merge_train) { create(:merge_train, merge_request: merge_request) }
+
+    before do
+      stub_licensed_features(merge_pipelines: true, merge_trains: true)
+      project.update!(merge_pipelines_enabled: true)
+      project.update!(merge_trains_enabled: true)
+    end
+
+    it 'has merge train entity' do
+      expect(subject.as_json[:merge_train]).to include(:index)
+      expect(subject.as_json[:merge_train]).to include(:user)
+      expect(subject.as_json[:merge_train]).to include(:pipeline)
+      expect(subject.as_json[:merge_train]).to include(:created_at)
+    end
+
+    it 'has merge train summary entity' do
+      expect(subject.as_json[:merge_trains_summary]).to include(:total_count)
+    end
+
+    context 'when the merge request is not on a merge train' do
+      let!(:merge_train) { }
+
+      it 'does not have merge_train entity' do
+        expect(subject.as_json).not_to include(:merge_train)
+      end
+    end
+
+    context 'when the merge train feature is disabled' do
+      before do
+        project.update!(merge_trains_enabled: false)
+      end
+
+      it 'does not have merge train summary entity' do
+        expect(subject.as_json).not_to include(:merge_trains_summary)
+      end
+    end
   end
 end
diff --git a/ee/spec/serializers/merge_train_entity_spec.rb b/ee/spec/serializers/merge_train_entity_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..03052849ef90696d19229d617ed8aa57e295964f
--- /dev/null
+++ b/ee/spec/serializers/merge_train_entity_spec.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MergeTrainEntity do
+  let(:merge_train) { create(:merge_train) }
+  let(:entity) { described_class.new(merge_train, request: request) }
+  let(:request) { double('request') }
+
+  before do
+    allow(request).to receive(:current_user).and_return(merge_train.user)
+  end
+
+  describe '#as_json' do
+    subject { entity.as_json }
+
+    it 'includes attributes' do
+      expect(subject[:index]).to eq(merge_train.index)
+      expect(subject[:user][:name]).to eq(merge_train.user.name)
+      expect(subject[:pipeline][:id]).to eq(merge_train.pipeline.id)
+      expect(subject[:created_at]).to eq(merge_train.created_at)
+    end
+  end
+end
diff --git a/ee/spec/serializers/merge_trains_summary_entity_spec.rb b/ee/spec/serializers/merge_trains_summary_entity_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..f5c93f6530915935b98fe0c015d36fb99c9556c8
--- /dev/null
+++ b/ee/spec/serializers/merge_trains_summary_entity_spec.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MergeTrainsSummaryEntity do
+  let(:merge_train) { create(:merge_train) }
+  let(:entity) { described_class.new(merge_train.merge_request) }
+
+  describe '#as_json' do
+    subject { entity.as_json }
+
+    it 'includes attributes' do
+      expect(subject[:total_count]).to eq(1)
+    end
+  end
+end