Alexander Gunn was born at Dunen, Isle of Skye on 6 September 1889, the son of John Douglas and Mary Gunn. He joined the Merchant Marine and served as an Ordinary Seaman in the SS MAGICIAN between May 1908 and July 1909. He then served in six different ships and then was the Third Officer of the SS BAROTSE from 30 January 1914 until 13 March 1915.

He joined the Royal Navy as a Temporary Sub Lieutenant, RNR on 22 April 1915. Alexander Gunn joined submarines on 15 May 1915 with an appointment to the Submarine Depot Ship HMS VULCAN. On 1 November 1915 he was appointed to HMS E26 as Navigating Officer. On 6 July 1916, E26 was lost with all hands. It is believed that the Submarine was mined whilst patrolling off the river Ems.

Alexander Gunn is commemorated on the Portsmouth Naval Memorial on Panel No. 22.