Jellicoe, John Rushworth Jellicoe, First Earl (1859–1935), a British naval officer. Jellicoe became a naval cadet in 1872 and was commissioned in 1880. He was commander of the Grand Fleet at the opening of World War I. In the Battle of Jutland (May 31–June 1, 1916), Jellicoe engaged the German High Seas Fleet in the largest naval battle of the war. The British suffered greater losses despite numerical superiority, but forced the German fleet to return to harbor.

Jellicoe was first sea lord and chief of the naval staff, 1916–17. He was made a viscount in 1918 and admiral of the fleet in 1919. Jellicoe was governor general of New Zealand, 1920–24. He retired from the Navy in 1924 and was made an earl in 1925.