Oliver Cummings Farrington (9 October 1864 Brewer, Maine, USA 2 November 1933 Chicago, Illinois, USA) was an American geologist. He was born at Brewer, Maine, and was educated at the University of Maine (B.S., 1881; M.S., 1888) and at Yale University (Ph.D., 1891), where he was tutor in 1890-91. Between 1882 and 1887 he taught science in various Maine academies, in 1893 he was an assistant in the United States National Museum, in 1894 he became curator geology in the Field Museum of Natural History, Chicago, and from 1894 to 1904 he was lecturer on mineralogy at the University of Chicago. He was a collaborator in mines and mineralogy at the Paris Exposition in 1900 and a member of the International Jury of Awards at St. Louis in 1904. He was the president of the American Association of Museums (now the American Alliance of Museums) in 1914–16.