Sir Alexander Ludovic Duff (20 February 1862 – 22 November 1933) was a Royal Navy officer who served as Commander-in-Chief, China Station.

He served in World War I as Rear-Admiral (Second-in-Command) of the 4th Battle Squadron from 1914 to 1916, taking part in the Battle of Jutland in 1916, where he flew his flag in HMS Superb.

Like the First Sea Lord, Admiral Jellicoe, Duff initially opposed the use of convoys.

[4] However, his efforts greatly reduced the destruction caused by the "underwater menace".

[5] In 1917 he became Assistant Chief of Naval Staff and then, from 1919, Commander-in-Chief, China Station.