Mariot Arbuthnot was a Royal Navy officer who served in the American War of Independence. In 1759, during the Seven Years' War, he commanded the Portland, one of the ships employed under Commodore Robert Duff in the blockade of Quiberon Bay, and was present at the total defeat of the French on 20 November. From 1775 to 1778, he was Resident Commissioner of the Navy, Halifax Nova Scotia. He was Lieutenant Governor of Nova Scotia, 1776–78. He was replaced in this role by Richard Hughes. It may have been about then that an armed schooner was named Arbuthnot after him. On 19 March 1779, he was made Vice-Admiral of the Blue, and on 2 May 1779 took command of HMS Europa. That same year he took up his appointment as commander-in-chief on the North American Station.

Soon after arriving at his destination, he was blockaded in New York City harbor by the French fleet under Count d'Estaing. In December 1779, Arbuthnot conveyed the troops of Sir Henry Clinton to Charleston, South Carolina, and cooperated with him in laying siege to that city. The surrender document signed by prominent citizens was addressed to him and Clinton. On 26 September 1780 he was promoted to Vice-Admiral of the White. On 13 March 1781, he fought the French Newport squadron, at the Battle of Cape Henry, before returning to England. He advanced by seniority to become, on 1 February 1793, Admiral of the Blue. He died in London the following year, leaving two sons, John and Charles.