Sir Nicholas John Hannen was a British barrister, diplomat and judge who served in China and Japan. He was the Chief Justice of the British Supreme Court for China and Japan from 1891 to 1900 and also served concurrently as Consul-General in Shanghai from 1891 to 1897. He was judge of the British Court for Japan from 1881 to 1891. He was the brother of James Hannen, a noted British judge of the 19th century. His son, Nicholas "Beau" Hannen was a famous actor of the early and mid-20th century.

The British Supreme Court for China was a court established in the Shanghai International Settlement to try cases against British subjects in China, Japan and Korea under the principles of extraterritoriality.