- Optometry
- Opus Dei
- Opus
- Oral History
- Oral Literature in English
- Oral Literature in French
- Orange Order in Canada
- Orange Shirt Day
- Orangeville
- Oratorio Composition
- Oratorio Performance
- Orchestra London Canada (now London Symphonia)
- Orchestral Composition
- Orchestral Music
- Orchestras Canada/Orchestres Canada
