diff --git a/app/assets/javascripts/behaviors/markdown/highlight_current_user.js b/app/assets/javascripts/behaviors/markdown/highlight_current_user.js
new file mode 100644
index 0000000000000000000000000000000000000000..6208b3f0032a1be6619f3936fae7266d285c20db
--- /dev/null
+++ b/app/assets/javascripts/behaviors/markdown/highlight_current_user.js
@@ -0,0 +1,17 @@
+/**
+ * Highlights the current user in existing elements with a user ID data attribute.
+ *
+ * @param elements DOM elements that represent user mentions
+ */
+export default function highlightCurrentUser(elements) {
+  const currentUserId = gon && gon.current_user_id;
+  if (!currentUserId) {
+    return;
+  }
+
+  elements.forEach(element => {
+    if (parseInt(element.dataset.user, 10) === currentUserId) {
+      element.classList.add('current-user');
+    }
+  });
+}
diff --git a/app/assets/javascripts/behaviors/markdown/render_gfm.js b/app/assets/javascripts/behaviors/markdown/render_gfm.js
index 429455f97ece77c447ca9001a9fe8a154e5b4a10..a2d4331b6d1b4ce03e3094a702387f016e4e74c7 100644
--- a/app/assets/javascripts/behaviors/markdown/render_gfm.js
+++ b/app/assets/javascripts/behaviors/markdown/render_gfm.js
@@ -2,6 +2,7 @@ import $ from 'jquery';
 import syntaxHighlight from '~/syntax_highlight';
 import renderMath from './render_math';
 import renderMermaid from './render_mermaid';
+import highlightCurrentUser from './highlight_current_user';
 
 // Render GitLab flavoured Markdown
 //
@@ -11,6 +12,7 @@ $.fn.renderGFM = function renderGFM() {
   syntaxHighlight(this.find('.js-syntax-highlight'));
   renderMath(this.find('.js-render-math'));
   renderMermaid(this.find('.js-render-mermaid'));
+  highlightCurrentUser(this.find('.gfm-project_member').get());
   return this;
 };
 
diff --git a/app/assets/javascripts/notes/components/notes_app.vue b/app/assets/javascripts/notes/components/notes_app.vue
index d8e8efb982a43821e4f9bbfb20a02172e2e05307..618a1581d8f6daac56b7f8d9aaf55e08adfced3b 100644
--- a/app/assets/javascripts/notes/components/notes_app.vue
+++ b/app/assets/javascripts/notes/components/notes_app.vue
@@ -11,6 +11,7 @@ import commentForm from './comment_form.vue';
 import placeholderNote from '../../vue_shared/components/notes/placeholder_note.vue';
 import placeholderSystemNote from '../../vue_shared/components/notes/placeholder_system_note.vue';
 import skeletonLoadingContainer from '../../vue_shared/components/notes/skeleton_note.vue';
+import highlightCurrentUser from '~/behaviors/markdown/highlight_current_user';
 
 export default {
   name: 'NotesApp',
@@ -96,6 +97,9 @@ export default {
       });
     }
   },
+  updated() {
+    this.$nextTick(() => highlightCurrentUser(this.$el.querySelectorAll('.gfm-project_member')));
+  },
   methods: {
     ...mapActions({
       fetchDiscussions: 'fetchDiscussions',
diff --git a/app/assets/stylesheets/framework/gfm.scss b/app/assets/stylesheets/framework/gfm.scss
index d2ba76f516016b447e9c1b070c768330ff3e5bf2..50d4298d418f1cdf4bf3f37b73a31f46a7374ae7 100644
--- a/app/assets/stylesheets/framework/gfm.scss
+++ b/app/assets/stylesheets/framework/gfm.scss
@@ -11,6 +11,10 @@
   padding: 0 2px;
   background-color: $blue-100;
   border-radius: $border-radius-default;
+
+  &.current-user {
+    background-color: $orange-100;
+  }
 }
 
 .gfm-color_chip {
diff --git a/changelogs/unreleased/winh-highlight-current-user.yml b/changelogs/unreleased/winh-highlight-current-user.yml
new file mode 100644
index 0000000000000000000000000000000000000000..125a5c08c4e1b59b8126904eb394ccb6e9f78d90
--- /dev/null
+++ b/changelogs/unreleased/winh-highlight-current-user.yml
@@ -0,0 +1,5 @@
+---
+title: Highlight current user in comments
+merge_request: 21406
+author:
+type: changed
diff --git a/spec/features/issues/notes_on_issues_spec.rb b/spec/features/issues/notes_on_issues_spec.rb
index f08c73f947cb0f9814f3ed556f802e92204f649c..fed77453cbb7d68d926450da6b1eb49502d3f9e8 100644
--- a/spec/features/issues/notes_on_issues_spec.rb
+++ b/spec/features/issues/notes_on_issues_spec.rb
@@ -3,6 +3,12 @@ require 'spec_helper'
 describe 'Create notes on issues', :js do
   let(:user) { create(:user) }
 
+  def submit_comment(text)
+    fill_in 'note[note]', with: text
+    click_button 'Comment'
+    wait_for_requests
+  end
+
   shared_examples 'notes with reference' do
     let(:issue) { create(:issue, project: project) }
     let(:note_text) { "Check #{mention.to_reference}" }
@@ -12,10 +18,7 @@ describe 'Create notes on issues', :js do
       sign_in(user)
       visit project_issue_path(project, issue)
 
-      fill_in 'note[note]', with: note_text
-      click_button 'Comment'
-
-      wait_for_requests
+      submit_comment(note_text)
     end
 
     it 'creates a note with reference and cross references the issue' do
@@ -74,4 +77,16 @@ describe 'Create notes on issues', :js do
       let(:mention) { create(:merge_request, source_project: project) }
     end
   end
+
+  it 'highlights the current user in a comment' do
+    project = create(:project)
+    issue = create(:issue, project: project)
+    project.add_developer(user)
+    sign_in(user)
+
+    visit project_issue_path(project, issue)
+    submit_comment("@#{user.username} note to self")
+
+    expect(page).to have_selector '.gfm-project_member.current-user', text: user.username
+  end
 end
diff --git a/spec/javascripts/behaviors/markdown/highlight_current_user_spec.js b/spec/javascripts/behaviors/markdown/highlight_current_user_spec.js
new file mode 100644
index 0000000000000000000000000000000000000000..3305ddc412d885274ddfc463e697557b674f23e7
--- /dev/null
+++ b/spec/javascripts/behaviors/markdown/highlight_current_user_spec.js
@@ -0,0 +1,55 @@
+import highlightCurrentUser from '~/behaviors/markdown/highlight_current_user';
+
+describe('highlightCurrentUser', () => {
+  let rootElement;
+  let elements;
+
+  beforeEach(() => {
+    setFixtures(`
+      <div id="dummy-root-element">
+        <div data-user="1">@first</div>
+        <div data-user="2">@second</div>
+      </div>
+    `);
+    rootElement = document.getElementById('dummy-root-element');
+    elements = rootElement.querySelectorAll('[data-user]');
+  });
+
+  describe('without current user', () => {
+    beforeEach(() => {
+      window.gon = window.gon || {};
+      window.gon.current_user_id = null;
+    });
+
+    afterEach(() => {
+      delete window.gon.current_user_id;
+    });
+
+    it('does not highlight the user', () => {
+      const initialHtml = rootElement.outerHTML;
+
+      highlightCurrentUser(elements);
+
+      expect(rootElement.outerHTML).toBe(initialHtml);
+    });
+  });
+
+  describe('with current user', () => {
+    beforeEach(() => {
+      window.gon = window.gon || {};
+      window.gon.current_user_id = 2;
+    });
+
+    afterEach(() => {
+      delete window.gon.current_user_id;
+    });
+
+    it('highlights current user', () => {
+      highlightCurrentUser(elements);
+
+      expect(elements.length).toBe(2);
+      expect(elements[0]).not.toHaveClass('current-user');
+      expect(elements[1]).toHaveClass('current-user');
+    });
+  });
+});