Admiral Marriot Arbuthnot (1711–31 January 1794) was son of Robert Arbuthnot and Sarah, née Bury, his father being son of Rev Robert Arbuthnot, minister of Chrichton & Cranston. He became an admiral of the British Royal Navy during the American War for Independence. He became a lieutenant in 1739, commander 1746 and post captain in 1747. In 1759 he commanded The Portland, one of the ships employed under Commodore Duff in the blockade of Quiberon Bay, and he was present at the total defeat of the French on 20 November. From 1775 to 1778 he was naval commissioner resident at Halifax, Nova Scotia. In 1779 he was made vice admiral, and commander-in-chief on the 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 he conveyed the troops of Sir Henry Clinton to Charleston, South Carolina, and cooperated with him in laying siege to that city. He advanced by seniority to become, in February 1793, admiral of the blue . He died in London the following year, leaving two sons, John and Charles.

He is thought to have been related to Dr. John Arbuthnot, the satirist and mathematician.