- O
- OO
- OO
- OO
- OOak
- OakOBE
- ObeObs
- ObsOcc
- OccOce
- OceOct
- OCTOdd
- OddODE
- ODEOdu
- OduOfe
- OfeOff
- OffOge
- OgeOh
- OhOHM
- OhmOja
- OjaOKA
- OKAOku
- OkuOla
- OlaOld
- OldOle
- OleOli
- OliOli
- OliOls
- OlsOma
- OmaOme
- OMEOmn
- OmnO
- OnaOne
- OneOne
- OneOne
- oneOni
- OniOno
- Onooof
- OogOpa
- OpaOpe
- OpeOpu
- OpuOra
- OraOrb
- OrbOrc
- OrcOre
- OreOrh
- OriOri
- OriOrl
- OrlOrp
- OrpOrq
- OrqOrt
- OrtOsa
- OsaOsc
- OscOsl
- OslOST
- OstOth
- OthOts
- OtsOtt
- OttOur
- OurOut
- OutOut
- OutOut
- OutOve
- OVEOvi
- OviOwe
- OweOxf
- Oxf
- OzaOzu
- Ozuozz
- Opatovský, Robo
- Opaz
- Opbrouck, Wim (Belgian actor & musician)
- Opća opasnost
- OPcrotte
- Opeia, Cazzi
- Opel, Billy
- Opel, Jackie
- Open
- Open Access (Polish power folk metal band)
- Open Air Stereo
- OPEN ARMS (UK Pop Band)
- Open Boundaries & Lazerpunk
- 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. Goldin
- Open Mike Eagle feat. Has-Lo
- Open Mike Eagle feat. Kool A.D.
- 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 Road (US bluegrass group)
- Open Sails
- Open Sea, The
- Open Season (Australian RAC band)
- Open Sky
- Open Skyz
- Open Space and Stars
- 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
- Opéra Bastille, Orchestre de l’, Chung, Myung-Whun
- Opéra de Nuit
- Opera Diabolicus (Doom/Black/Death Metal Swedish Band)
- Opera Familia
- Opera IX
- Opera Magna
- Opera Magna feat. Marta Barbé
- Opera Multi Steel
- OperaBabes
- Operación Triunfo (fake artist)
- Operación Triunfo
- Operación Triunfo 2009
- Operación Triunfo 2017
- Operación Triunfo 2018
- Operación Triunfo, Academia
- Operaciya Plastilin
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operatika (symphonic metal)
- Operating Tracks, The
- Operating Tracks, The feat. Rein
- Operation
- Operation Cunt Destroyer (Scottish slam/brutal death metal/deathcore)
- 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 (British indie rock band)
- Operators, The (ska, from Indianapolis, IN)
- Operelly
