- O
- OO
- OO
- OOak
- Oak
- ObaObo
- OboOce
- OceOch
- OchOct
- OctOdd
- OddOdi
- OdiOf
- ofoff
- OffOGR
- OGROh
- OhOik
- OilOk
- okOko
- Oko
- Old
- OldOle
- OleOli
- OliOll
- OllOly
- OlyOmd
- OMDOmn
- OmnOnc
- OncOne
- OneOne
- OneOne
- OneOnl
- OnlOny
- OnyOPc
- OpeOph
- OphOR
- OrOrb
- OrbOrc
- OrcOre
- OreOri
- OriOri
- OriOrm
- OrmOrq
- OrqOrt
- OrtOs
- OsOsc
- OscOsm
- OsmOsu
- OsuOti
- OtiOtt
- OttOur
- OurOut
- OutOut
- OutOv
- OVOve
- OveOWE
- OweOwl
- OwmOyo
- OysOzu
- Ozuozz
- Opeia, Cazzi
- Opel, Billy
- Opel, Jackie
- Open
- Open Air Stereo
- OPEN ARMS (UK Pop Band)
- Open Circle, The (Belgian dub techno producer)
- Open City (Punk Hardcore)
- Open Door
- Open Fifth
- Open Hand (American indie rock band)
- Open Letter, An
- Open Mike Eagle (US rapper and comedian)
- Open Mike Eagle & White, Paul
- Open Mike Eagle feat. Alpha MC
- Open Mike Eagle feat. Buress, Hannibal
- Open Mike Eagle feat. Has-Lo
- Open Mike Eagle feat. Kool A.D.
- Open Mike Eagle feat. Megabusive & McGee, Finiki
- Open Mike Eagle feat. Serengeti
- Open Mike Eagle feat. Still Rift and Video Dave
- Open Mike Eagle feat. Toy Light
- Open Mike Eagle feat. Video Dave and Still Rift
- Open Mike Eagle feat.Brown, Danny
- Open Mind, The (68–73 UK psychedelic rock band)
- Open Minded
- Open Palms
- Open Sails
- Open Sea, The
- Open Season (Australian RAC band)
- Open Sky
- Open Skyz
- Open the Skies
- Open University, The
- Open Up and Bleeds, The
- Open, The
- OpenBSD
- Openside
- Opensight (Metal)
- Opensouls
- Opera (Polish group)
- Opera (Italian hard trance project)
- Opera Australia
- Opera Diabolicus (Doom/Black/Death Metal Swedish Band)
- Opera Familia
- Opera IX
- Opera Magna
- OperaBabes
- Operación Triunfo (fake artist)
- Operación Triunfo 2017
- Operación Triunfo 2018
- Operación Triunfo, Academia
- Operaciya Plastilin
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operatica
- Operatika (symphonic metal)
- Operating Tracks, The
- Operating Tracks, The feat. Rein
- Operation
- Operation Ivy
- Operation M.D, The
- Operation Mindcrime
- Operation Ratification
- Operation Sodasteal (kaj strife & slaney(in)famous)
- Opération Zéro
- Operation, The
- Operation, The (predecessor to mewithoutYou)
- Operator (Hard Rock Band)
- Operator Please
- Operator, Hello
- Operators (Canadian band)
- Operators, The (ska, from Indianapolis, IN)
- Operus
- Opeth (Swedish progressive metal/rock)
- Opgeduveld
- Opgezwolle (Dutch rap group)
- Opgezwolle feat. Vrieling, Bert
- Ophanin
- Ophelia Ragtime Orchestra
- Ophelia's Eye (Melodic death metal band from Switzerland)
- Opheliac
- Ophelias, The (psychedelic rock band from San Francisco)
- Ophelias, The (Cincinnati indie rock band)
- Ophidian (hardcore dj)
- Ophidian & Playah, Tha
- Ophidian Ascension, The (Australian death metal)
- Ophidian I
- Ophidian Memory
- Ophis (Germany, Metal)
