O
- Billy Ocean (3)
- Sinéad O'Connor (1)
- Alan O'Day (1)
- Colby O'Donis (1)
- Ohio Players (2)
- The O'Jays (1)
- Olivia (1)
- 112 (1)
- Roy Orbison (2)
- Tony Orlando and Dawn (3)
- Donny Osmond (1)
- The Osmonds (1)
- Gilbert O'Sullivan (1)
- Outkast (3)
- Owl City (1)
Read more about this topic: List Of Artists Who Reached Number One In The United States