- O'Brian, Hugh
- O'Brien, Conan
- O'Brien, Edmond
- O'Brien, Pat
- O'Brien, Richard
- O'Connell, Charlie
- O'Connor, Carroll
- O'Connor, Donald
- O'Connor, Kevin J.
- O'Donnell, Keir
- O'Halloran, Brian
- O'Halloran, Jack
- O'Hanlon, Ardal
- O'Hara, David
- O'Hare, Denis
- O'Hare, Michael
- O'Hurley, John
- O'Keefe, Michael
- O'Leary, Matt
- O'Loughlin, Alex
- O'Mara, Jason
- O'Neal, Patrice
- O'Neal, Ryan
- O'Neill, Con
- O'Quinn, Terry
- O'Regan, James
- O'Reilly, Robert
- O'Shea, Milo
- O'Toole, Peter
- Oates, Warren
- Oberoi, Vivek
- Ochoa, Ryan
- Oconnell, Jerry
| - Odenkirk, Bob
- ODonnell, Chris
- Offerman, Nick
- Oka, Masi
- Okamura, Gerald
- Oldman, Gary
- Olin, Ken
- Oliver, Barret
- Olivier, Laurence
- Olmos, Edward James
- Olsen, Eric Christian
- Olsson, Ty
- Olyphant, Timothy
- Oneill, Ed
- Ontkean, Michael
- Orbach, Jerry
- Orser, Leland
- Ortiz, John
- Ortiz, Shalim
- Ortiz, Tito
- Osbourne, Jack
- Osment, Haley Joel
- Osmond, Ken
- Ostrum, Peter
- Oswalt, Patton
- Ovenden, Julian
- Overton, Rick
- Owen, Clive
- Owen, Lloyd
- Owens, Chris
- Owens, Gary
- Oz, Dr. Mehmet
- Oz, Frank
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