Roger Sherman Loomis (October 31, 1887 – October 11, 1966) was an American scholar and one of the foremost authorities on medieval and Arthurian literature.
Roger Sherman Loomis was the son of Henry Loomis and Jane Herring Greene, the great nephew of William Maxwell Evarts and the great-great grandson of American founding father Roger Sherman. Born in Yokohama, Japan, he was educated at The Hotchkiss School Lakeville, Connecticut.
He earned a B.A. from Williams College in 1909, an M.A. from Harvard University in 1910, and was a Rhodes Scholar at New College, Oxford University in 1913. He held honorary degrees from Columbia, Williams, the University of Wales and the University of Rennes in France.
He was an instructor at the University of Illinois at Urbana from 1913 to 1918. During World War I he edited an Army publication Atenshun 21. He left Illinois for Columbia University, where he taught from 1919 until 1958: he was a member of Columbia's English faculty and held an emeritus position there from 1958 until his death in 1966. In 1919, also, Loomis married his first wife, Gertrude Schoepperle Loomis, (1882-1921), a medieval scholar who shared his interest in Arthurian literature. (Folklore 38.4 1927 405–407).
From his early years he studied the influence of Celtic mythology on Arthurian legend, especially the Holy Grail romance. In 1930 Loomis attended the first International Arthurian Congress in Truro, Cornwall, where he and other scholars investigated Arthurian legends. He was a member of the International Arthurian Society (president of American Branch, 1948 – 63), the Modern Language Association, the Mediaeval Academy of America (fellow; second vice-president, 1961 – 64), the Modern Humanities Research Association and the American Humanist Association. In 1955-6 he was an Eastman Professor at Oxford University.