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- Prentiss Oakley (1905–1957) Bienville Parish sheriff, 1940–1952; previously part of the posse that ambushed Bonnie and Clyde in 1934
- Alton Ochsner (1896–1981) surgeon, medical researcher
- Robert Fred "Bob" Odom (born 1935) Agriculture commissioner (1980–2008)
- Henry Warren Ogden (1842-1905) politician
- Taylor W. O'Hearn (1907–1997) politician
- B.F. O'Neal, Jr., (1922–2004) politician
- Joe "King" Oliver (1885–1938) jazz musician
- Virgil Orr (born 1923) state representative, Louisiana Tech University vice president
- Joe Osborn (born 1937) musician
- Lee Harvey Oswald (1939–1963) presumed assassin of U.S. President John Kennedy
- W. Darrell Overdyke (1907–1973) historian
- John H. Overton (1875–1948) US Senator
- Mel Ott (1909–1958) baseball player
- Don Owen (1930-2012) broadcaster and politician
Read more about this topic: List Of People From Louisiana