- Ogechi (Vivian) Nwadiaru
- Oguzhan Alagoz
- Ohad Eisenhandler
- Ohio State University Student Chapter
- Okan Arslan
- Oklahoma State University Student Chapter
- Ola Batarseh
- Ola Jabali
- Olaf Jahn
- Oleg A. Prokopyev
- Oleg Gusikhin
- Oleksandr Akulov
- Olga Bagatourova
- Olga Raskina
- Olivia Natan
- Olivia Sheng
- Olivier Allais
- Olivier Toubia
- Olvi Mangasarian
- Olympic Games
