- O
- OO
- OO
- OO
- OOak
- OakOas
- OasObi
- ObiObs
- ObsOce
- OceOce
- OceOct
- OctOda
- ODAOdd
- OddOd
- OdiOdy
- OdyOfe
- OfeOFF
- OffOgd
- Ogdoh
- OhOhg
- OhhOis
- OisOKA
- OkaOkl
- OklOla
- OlaOld
- OldOle
- OleOle
- OLFOli
- OliOli
- OliOls
- OlsOma
- OmaOme
- OmeOmn
- OmnOn
- On
- OndOne
- OneOne
- OneOne
- OneOnk
- OnkOno
- OnoOoh
- OohOpa
- OpaOpe
- OpeOpr
- OPROra
- OraOra
- ORBOrc
- OrcOrc
- OrcOre
- OreOri
- Ori
- OriOrl
- OrlOro
- OroOrq
- OrqOrt
- OrtOs
- OsOsb
- OsbOsi
- OsiOso
- OsoOsw
- OswOti
- OtiOtt
- Ott
- Our
- OurOut
- OutOut
- OutOut
- OutOve
- OveOve
- OVEOwe
- OweOwm
- OwnOxy
- OxyOzi
- Oziozz
- Opambuo International Band of Ghana
- Opania, Marian
- Opanije
- Opatovský, Robo
- 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 Fifth
- Open Hand (American indie rock band)
- Open House (Celtic folk 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. Ferreira, R.A.P., Still Rift and Video Dave
- Open Mike Eagle feat. Has‐Lo
- Open Mike Eagle feat. Kool A.D.
- Open Mike Eagle feat. Nocando & Barman, Paul, MC
- Open Mike Eagle feat. Serengeti
- 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 the Door for Three
- Open the Skies
- Open Trench
- Open University, The
- Open Up and Bleeds, The
- Open, The
- OpenBSD
- Openside
- Opensight (Metal)
- Opensouls
- Opera (Polish group)
- Opera (Italian hard trance project)
- Opera Alaska
- Opera Australia
- Opéra Bastille, Orchestre de l’, Chung, Myung-Whun
- Opera Chaotique
- 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 2009
- Operación Triunfo 2017
- Operación Triunfo 2018
- Operación Triunfo 2023
- Operación Triunfo 2025 (OT Series 13)
- Operación Triunfo, Academia
- Operaciya Plastilin
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operatika (symphonic metal)
- Operating Tracks, The
- Operating Tracks, The feat. Anitchka, Emma
- Operating Tracks, The feat. Rein
- 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)
- Operation Winter Mist
- Opération Zéro
- Operation, The
- Operation, The (predecessor to mewithoutYou)
