lmao...could have added female but "actor" tends to be male-- think that's why half the list is male. Female is fine as they are referred to as actors from time to time 
13 Actors that start with the letter O, first or last name.
1. Owen Wilson
2. Orlando Bloom
3. Ryan O'neil
4. Gary Oldman
5. Laurence Olivier
6. Omar Epps
7. Oliver Reed
8. Ashley Olsen
9. Omar Sharif
10. Hayley Joel Osment
11. Mary-Kate Olsen
12. Jerry O'Connell