diff --git a/lib/shared/markdown.js b/lib/shared/markdown.js
--- a/lib/shared/markdown.js
+++ b/lib/shared/markdown.js
@@ -347,6 +347,8 @@
   );
 }
 
+const ensRegex: RegExp = /^[a-zA-Z0-9-]{3,}\.eth$/;
+
 export {
   paragraphRegex,
   paragraphStripTrailingNewlineRegex,
@@ -372,4 +374,5 @@
   stripSpoilersFromNotifications,
   stripSpoilersFromMarkdownAST,
   parseChatMention,
+  ensRegex,
 };
diff --git a/lib/shared/markdown.test.js b/lib/shared/markdown.test.js
--- a/lib/shared/markdown.test.js
+++ b/lib/shared/markdown.test.js
@@ -1,6 +1,6 @@
 // @flow
 
-import { spoilerRegex } from './markdown.js';
+import { spoilerRegex, ensRegex } from './markdown.js';
 import { chatMentionRegex } from './mention-utils.js';
 
 // Each of the below tests is subject to the following RegEx pattern:
@@ -141,4 +141,40 @@
     expect('@[256|1:test]]').not.toMatch(chatMentionRegex);
     expect('@[[256|1:test]').not.toMatch(chatMentionRegex);
   });
+
+  describe('ensRegex', () => {
+    it('should match all valid ENS names', () => {
+      expect('foo.eth').toMatch(ensRegex);
+      expect('jack.eth').toMatch(ensRegex);
+      expect('thisuserhasareallylongname.eth').toMatch(ensRegex);
+    });
+
+    it('should not match any usernames names less than 3 characters', () => {
+      expect('fo.eth').not.toMatch(ensRegex);
+      expect('a.eth').not.toMatch(ensRegex);
+      expect('.eth').not.toMatch(ensRegex);
+    });
+
+    it('should not match any usernames with spaces', () => {
+      expect('foo bar.eth').not.toMatch(ensRegex);
+      expect('user1.eth user2.eth').not.toMatch(ensRegex);
+      expect('user1.eth and user2.eth').not.toMatch(ensRegex);
+    });
+
+    it('should not match any usernames with underscores', () => {
+      expect('foo_bar.eth').not.toMatch(ensRegex);
+      expect('_user1.eth').not.toMatch(ensRegex);
+    });
+
+    it('should not match any usernames without .eth', () => {
+      expect('foo').not.toMatch(ensRegex);
+      expect('ryan.eth2').not.toMatch(ensRegex);
+    });
+
+    it('should not match any usernames with special characters', () => {
+      expect('foo.eth!').not.toMatch(ensRegex);
+      expect('foo.eth#').not.toMatch(ensRegex);
+      expect('foo$.eth').not.toMatch(ensRegex);
+    });
+  });
 });