Harry Ambrose Sylvester (January 19, 1908 – September 26, 1993) was an American short-story writer and novelist in the first half of the 20th century. His stories were published in popular magazines such as Collier's, Esquire and Commonweal, publishing over 150 short stories. Some of his stories were published in a collection entitled All Your Idols in 1948 and in several other short story anthologies. Among his novels were Dearly Beloved (1942), Dayspring (1945), and Moon Gaffney (1947). He was credited with 'original screen story', along with John Steinbeck and Alfred Hitchcock, for Hitchcock's Lifeboat (1944). A version of this story was published in Collier's in 1942.
Sylvester was born in Brooklyn, New York in 1908 and went to Notre Dame, playing football for Knute Rockne, graduating in 1930 with a degree in journalism. He soon found work as a correspondent for the New York Evening Post and a reporter for the New York Herald Tribune. He was a friend and correspondent of Ernest Hemingway in the 1930s; several letters to him from Hemingway appear in the latter's Selected Letters. By mid-century, he was considered to be a very promising writer in Catholic circles but by the time of his death in 1993 he was virtually forgotten. He criticized the Catholic hierarchy heavily in several of his novels and dedicated Moon Gaffney to a group of "good Catholic radicals." He eventually renounced his faith and, with his second wife, became a Quaker. He didn't write a novel after 1950 and worked for the US Information Service for twenty years, spending the last 40 years of his life in the Washington, DC area.
His novel Dayspring was inspired by his trips to New Mexico. The University of New Mexico, University Libraries, Center for Southwest Research has a collection of bibliographic material and book reviews by and about Sylvester (and Willa Cather). However, his complete papers are housed in Georgetown University Library's Special Collections, and include correspondence, manuscripts and an unpublished work, Watch in the Night.