The Rev. Endicott Peabody (30 May 1857 - 17 November 1944) was the American Episcopal priest who founded Groton School for Boys (known today simply as Groton School), (in Groton, Massachusetts), in 1884. Peabody served as headmaster at Groton School from 1884 until 1940, and also served as a trustee at Lawrence Academy at Groton. In 1926 Peabody also founded Brooks School, which was named for 19th-century clergyman Phillips Brooks, a well-known preacher and resident of North Andover. Peabody was Franklin Delano Roosevelt's headmaster at Groton, and he officiated at FDR's marriage to Eleanor Roosevelt.
In 1882 during his first year at the Episcopal Theological School in Cambridge, Massachusetts (now the Episcopal Divinity School) Peabody, a seminarian not yet a priest, was invited to take charge of a little Episcopal congregation in Tombstone, Arizona (now St. Paul's Episcopal Church, Tombstone). After a long and tortuous trip, Peabody arrived in Tombstone two months after the "Gunfight at the O.K. Corral". He had words of praise for Wyatt Earp. Though he spent no more than six months in Tombstone he succeeded in getting the church built, St Paul's Episcopal Church. This church building today is the oldest in the state not belonging to the Roman Catholic Church. He was impressive physically, never losing a boxing match. He began a baseball team in Tombstone. He raised money by walking into the saloons and holding out his hat at the gambling tables. He has been spoken of as patron saint of the Episcopal Diocese of Arizona. The importance of this brief moment in his life, recorded in his diaries and correspondence, is that it helps describe the spirit and the presence of the man who was the great headmaster of Groton.