William Markle Berlin (March 29, 1880 – October 14, 1962) was an American businessman and politician who served as a Democratic member of the U.S. House of Representatives from Pennsylvania for two terms from 1933 to 1937.
He served as assistant librarian of the United States House of Representatives from February 1, 1957, until 1961 when promoted to librarian, and served in that capacity until his death in Greensburg, Pennsylvania.