Admiral of the Fleet Rosslyn Erskine Wemyss, 1st Baron Wester Wemyss (12 Apr 1864 – 24 May 1933) was a Royal Navy officer. During the First World War he served as commander of the 12th Cruiser Squadron and then as Governor of Moudros before leading the British landings at Cape Helles and at Suvla Bay during the Gallipoli Campaign. He was Commander of East Indies Egyptian Squadron in January 1916 and then First Sea Lord in December 1917.