- Operator
- Operator Please
- Opereiras
- Opeth
- Ophidian I
- Ophthalamia
- Opiate For The Masses
- Opick
- Opie Gone Bad
- Opihi Pickers
- Opium
- Opm
- Oppenheimer
- Opposing Motion
- Opposite Zero
- Oppressed
- Opressor
- Opshop
- Optiganally Yours
- Optimus Rhyme
- Opus
- Opus Iii
- Opus Orange
- Opwekking
- Or Just Not
- Oragic
- Oran Juice Jones
- Orange
- Orange 9mm
- Orange And Lemons
- Orange Blue
- Orange Caramel
- Orange Goblin
- Orange Is The New Black
- Orange Juice
- Orange Range
- Orange Seabones
- Orange Sky
- Oranssi Pazuzu
- Oratory
- Orba Squara
- Orbis Tertius
- Orbit
- Orbital
- Orbital Frame
- Orca Team
- Orcatastrophe
- Orchard
- Orchestra Baobab
- Orchestral Manoeuvres In The Dark