Oscar Kelly 'OK' Allen (1882 - 1936) was the Democratic Governor of Louisiana from 1932 to 1936, and was the successor to Alvin Olin King. Allen was a key cog in the political machine of Huey Long that dominated Louisiana during the first half of the 1930s.

Allen was born in Winn Parish, Louisiana on August 8, 1932. Allen took an early and active interest in politics and civic affairs. Allen was elected to the Lousiana State Senate in 1928 in the wake of Huey Long landslide victory in the gubernatorial election. Allen also served as Chairman of the Louisiana Highway Commission from 1928 until 1930 when the Louisiana State Supreme Court ruled that holding both legislative and executive positions was unconstitutional.

Allen was elected Governor of Louisiana in 1932. Allen did nothing to distinguish himself as Governor as the state was run by Huey Long from a distance in Washington, D.C.. Allen merely served as an instrument to carry through Long's wishes, earning the nickname OK Allen for his approval of all of Long's intended measures. There is one story, undoubtedly false but valuable for the perception of Allen that it demonstrates, that a leaf blew into OK Allen's office one day and that he signed it, thinking it was legislation from Long.

Allen died on January 28, 1936.