Admiral John Markham, (13 June 1761 – 13 February 1827) was a Royal Navy officer.
As a junior officer he served in the American Revolutionary War.
He commanded the third-rate HMS Hannibal in the action of 10 April 1795 and then the third-rate HMS Centaur, capturing a French frigate squadron in the action of 18 June 1799, during the French Revolutionary Wars.
He went on to be a Lord Commissioner of the Admiralty and First Naval Lord under Earl St Vincent.