- Olympic theme song
- Olympic Truce
- Olympic village
- Olympic Winter Games
- Olympic Youth Camp
- Olympiodorus
- Olympism
- Olympus Camera
- Olympus Mons
- olynthus
- O&M
- OMA
- O magnitude
- Omaha
- Omaheke
- Omalizumab
- Oman Drama
- Omanis
- Oman People's Uprising of Resistance Against Britain
- Omar Abu Risha
- Omar Bongo
- Omar Daoud
- Omar Hassan Ahmed al-Bashir
- Omar Khayyam
- Omar Khayyam crater