HMS E11 was an E-class submarine of the Royal Navy launched on 23 April 1914. E11 was one of the most successful submarines in action during the 1915 naval operations in the Dardanelles Campaign, sinking over 80 vessels of all sizes in three tours of the Sea of Marmara.

The British E-class submarines started out as improved versions of the British D-class submarine. The E class served with the Royal Navy throughout World War I as the backbone of the submarine fleet. The last surviving E class submarines were withdrawn from service by 1922.