O
- Shauna O'Brien
- Tim O'Connor (actor)
- Randy Oglesby
- Akio Ĺtsuka
- Ken Olandt
- David Oliver (actor)
- Heather Lauren Olson
- Tricia O'Neil
- Alan Oppenheimer
- Terry O'Quinn
- Robert O'Reilly
Read more about this topic: List Of Star Trek: The Next Generation Cast Members