| Author Name | Profession | Nationality |
| Oded Fehr | Actor | Israeli |
| Odysseas Elytis | Writer | Greek |
| Oksana Baiul | Athlete | American |
| Olafur Eliasson | Artist | Danish |
| Oliver Evans | Inventor | American |
| Oliver Hardy | Actor | American |
| Oliver Kahn | Athlete | German |
| Oliver St. John | Statesman | English |
| Olivia De Havilland | Actress | American |
| Omar Epps | Actor | American |
| Omar Khayyam | Poet | |
| Oriana Fallaci | Journalist | Italian |
| Orlando A. Battista | ||
| Orlando Cepeda | ||
| Orlando Gibbons | Composer | English |
| Orlando Jones | Comedian | American |
| Orrin Hatch | Politician | |
| Orson Scott Card | Writer | American |
| Osama Bin Laden | Criminal | |
| Osbert Lancaster | Cartoonist | English |
| Oscar Hammerstein | Writer | American |
| Oscar Hammerstein Ii | Musician | American |
| Ossie Davis | Actor | American |
| Otto Bauer | Writer | Austrian |
| Otto Hahn | Scientist | German |
| Otto Hermann Kahn | Businessman | German |
| Otylia Jedrzejczak | Athlete | Greek |
| Owen Feltham | Author | British |
| Owen Glendower | Royalty | Welsh |
| Owen Hart | Entertainer | Canadian |
“It is almost impossible to imagine that any one could be so insensible to the high morality of Mr. Mill's character as to suggest to him any course of conduct that was not entirely upright and consistent.”
