- Caes Vadios (Punk-Rock-Portugal) - Other name : ex-Os Cães, A Morte E O Desejo
- Os Cascavelletes (Rock'n'Roll-Brazil)
- Os Catalépticos (Psychobilly-Brazil)
- Os Golpes (Pop Rock-Portugal)
- Os Lobos (Psychedelic Rock-Brazil)
- Os Mutantes (Psychedelic Rock-Brazil) - Other name : O'Seis
- Os Pontos Negros (Indie Rock-Portugal)
- Os Porto (Pop Rock-Portugal)
- Os Tornados (Rock'n'Roll-Portugal)
- Os Velhos (Rock'n'Roll-Portugal)
- Os' Almirantes (Ska-Punk-Panama) - Other name : Los Chispines
- Osaka Popstar (Punk-Rock-USA)
- Osamu Kitajima (Prog Folk-Japan) - Other name : Osamu
- Osanna (Progressive Rock-Italy)
- Oresund Space Collective (Space Rock-Other) - Other name : OSC / Øresund Space Collective
- Oscar Suave (Psychedelic Rock-United-Kingdom)
- Oscil (Progressive Rock-France)
- Osiris The Rebirth (Space Rock-United-Kingdom) - Other name : Osiris
- Osker (Punk-Rock-USA)
- Oslow (Pop Rock-France)
- Osmosis (Psychedelic Rock-France)
- Hydra (Southern Rock-USA) - Other name : ex-Noah Mayflower, ex-Osmosis
- Old School (Pop Rock-France) - Other name : OSPbb
- Ostbrut (Street Punk - Oi-Germany)
