Admiral Sir John Reginald Thomas Fullerton, GCVO, CB (10 August 1840 – 29 June 1918) was a Royal Navy officer and courtier.

From 18 August to 14 December 1864 he was an Additional Lieutenant in HMS Bombay, an elderly 84-gun second rate ship of the line, cruising the coast of South America.

[3] The ship was destroyed in an accidental fire during target practice near Flores Island in the River Plate, off Montevideo, with the loss of some ninety officers and men.

[4] In 1865 he joined HMS Narcissus, a wooden-hulled screw frigate, still on the South America station, and on 10 March 1870, still a Lieutenant, was posted to the new corvette Volage in the Channel Squadron.

[7] In 1875 Fullerton joined the royal yacht HMY Victoria and Albert as second-in-command under Hugh Cambell, who died of typhoid fever on 12 February 1877.