| 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 |
“Men are mortal. So are ideas. An idea needs propagation as much as a plant needs watering. Otherwise both will wither and die.”
“Five years of Republicans' failed energy policies have resulted in Americans paying twice as much at the pump as they did in 2001, while big oil companies make triple the profits.”