Oscar Kelly Allen, Sr. (August 8, 1882 January 28, 1936), also known as O. K. Allen, was the 42nd Governor of Louisiana from 1932 to 1936. He was a key lieutenant in the political machine of Huey Pierce Long, Jr., that dominated the state during the first half of the 1930s. Allen succeeded Alvin Olin King, who served briefly in the state's highest office after Long left the governorship to take a seat in the United States Senate.