Archibald Algernon Henry St. Maur, 13th Duke of Somerset (né Seymour; 30 December 1810 – 10 January 1891) was an English aristocrat.
He was born at is family's home on Park Lane, Mayfair, the second son of Edward St. Maur, 11th Duke of Somerset and Lady Charlotte Douglas-Hamilton.
His motto, Foy Pour Devoir "Faith for Duty", has been adopted by HMS Somerset (IV) by permission.
He was baptized on 17 June 1811 at St. George's, Hanover Square, London,[1] and in 1885 succeeded his elder brother Edward Seymour, 12th Duke of Somerset, whose sons predeceased him.
Archibald died at his London home at 28 Berkeley Square,[4] unmarried and childless.