John Gray (12 December 1819 – 25 November 1872) was a Scottish merchant seaman and master mariner who served as Captain of the SS Great Britain for eighteen years.

[6] Gray progressed to commanding ships for Gibbs, Bright & Co.[6] He took both a demotion and a pay cut in order to serve as Second Officer on their SS Great Britain in 1852, in time for the vessel's first voyage to Australia.

[5] He held the longest tenure of any SS Great Britain captain, and in that role completed 27 journeys from the United Kingdom to Australia and back.

He knew how to handle his ship, his crew and his passengersOn his two penultimate voyages to Australia and back, Gray, according to subsequent newspaper reports:[6] suffered severely from liver and stomach complaint, brought on by pure anxiety to maintain the reputation of his ship in the strong competition with the London steam clippersOn 25 November 1872, thirty days into another return voyage from Melbourne to Liverpool,[12] Gray complained of pain in his bowels and returned to his cabin.

[2] Since there was no way to send a message ashore, his wife Mary Ann (née Jamieson) only found out that she was a widow when she and one of their daughters met the ship upon its arrival in Liverpool in January 1873.