O
- Olomidé, Koffi
- OM
- OMD
- Omega
- One Way System
- Only Living Witness
- Only Ones, The
- Onyx
- Operation Ivy
- Opeth
- Opus
- Opus lll
- Orange Goblin
- Orange Juice
- Orb, The
- Orbison, Roy
- Orbit, William
- Orbital, The
- Oregon
- Orchestra Baobab
- Orchid
- Orioles, The
- Orion The Hunter
- Orleans
- Orphaned Land
- Orton, Beth
- Oryema, Geoffrey
- Orzabal, Roland
- Os Mutantes
- Osanna