HMS R8 was a British R class submarine built by Vickers Limited at Barrow-in-Furness. She was laid down on 1 November 1917 and launched on 28 June 1918. R8 was commissioned on 26 July 1918. She came too late to see any combat in World War I, like most of the other R class submarines. In the Navy List for November 1918 she was based at Donegal. R8 was sold on 21 February 1923 to E. Suren.