HMS B11 was the last of 11 B-class submarines built for the Royal Navy in the first decade of the 20th century. Completed in 1906, it is best known for carrying out a successful attack on the Ottoman battleship Mesûdiye in the Dardanelles, an action for which her captain received the Victoria Cross. It spent the remainder of its active life serving in the Mediterranean, being converted into a surface patrol boat late in the war. B11 was sold for scrap in 1919.