- Osgoode Hall
- Osgoode, William
- Oshawa
- Osler, sir William
- Osmar R. Zaiane
- Osoyoos
- Ossie Michelin
- Ostanek, Walter
- Ostell, John
- Ostenso, Martha
- Osteoporosis Breakthrough
- Ostry, Sylvia
- Osuitok Ipeelee
- OTAN (Organisation du traité de l'Atlantique Nord)
- Otaries et phoques
- Ottawa
- Ottawa and Alberta Head for Emissions Control Showdown
- Ottawa Apologizes to Natives
- Ottawa Appeals Pay Equity Ruling
- Ottawa Ballet
