O
- Willis O'Brien – film special-effects artist
- Lefty O'Doul – baseball player
- Dagmar Oakland – stage and screen actress
- Mary-Kate and Ashley Olsen – actresses and entrepreneurs
- Omarion – musician
- Tatum O'Neal – actress
- Haley Joel Osment – actor
- Christi O'Connor – television journalist
Read more about this topic: List Of People From California