- O
- OO
- OO
- OOak
- OakObe
- Obs
- ObsOce
- OceOck
- OckOcu
- OcuODE
- OdeOdo
- OdoOfe
- OfeOff
- OffO
- OGXOHE
- OhGOJ
- OJOka
- OkaOl
- OlOld
- OldOle
- OleOli
- OliOli
- OliOLU
- OluOmb
- OmbOmn
- OmnOna
- OOne
- OneOne
- OneONE
- ONEOnl
- Onlooi
- OoiOpe
- OpeOpp
- OppOra
- OraOrb
- OrbOrc
- OrdOrg
- OrgOri
- OriOrl
- OrlOrp
- OrpOrt
- OrtOs
- OsOsc
- OscOsm
- OsmOT
- OTOtr
- OtrOtt
- OttOur
- OurOut
- OutOut
- OutOve
- OveOvi
- OviOwe
- OweOxo
- OxoOzr
- OZROZZ
- Ooi, Imee
- OOJA, Ms. (hiphop)
- Oojami
- Ookay
- Ookla the Mok (filk group)
- Ooklah the Moc
- Öökülm
- Oolacile
- Oolong (LI emo)
- oomiee
- Oomori, Kinuko (Japanese singer)
- Oomori, Seiko (Japanese pop/rock singer-songwriter)
- Oomph!
- Oomph! feat. Adel, den, Sharon
- Oomph! feat. Apocalyptica
- Oomph! feat. Hagen, Nina
- Oomph! feat. Harms, Chris
- Oomph! feat. Jandová, Marta
- Oomph! feat. L'ÂME IMMORTELLE
- Oomph! feat. L’Âme Immortelle
- Oompie Koerier
- Oona (Graphic artist born Oona Leganovic)
- Oona (Oona Garthwaite and Dave Tweedie)
- Oonagh (Senta-Sofia Delliponti)
- Oonagh feat. Björn
- Oonagh feat. Celtic Woman
- Oonagh feat. Fischer, Helene
- Oonagh feat. Safri Duo
- Oonagh feat. Santiano
- OoOo
- oOoOO (witch house/electronic producer)
- öOoOoOoOoOo
- Ooopopoiooo
- oop, anna
- Oopopi Symphony Orchestra
- Oorah (Orthodox Jewish Outreach Organization)
- Oordaya (aka Clara Guenot)
- Oorka
- Oort, Bart van (pianist)
- Oôs Joôs (West-Frisian rock & roll group, performing songs in dialect)
- Öösorr
- Oosterhuis, Trijntje
- Oosterhuis, Trijntje & Metropole Orkest
- Oosterhuis, Trijntje feat. Clayton–Hamilton Jazz Orchestra, The
- Oosterhuis, Trijntje feat. Dulfer, Candy
- Oosterhuis, Trijntje met Kraayenhof, Carel en Jansen, Janine
- Oosterhuis, Trijntje met McComb, Frank
- Oosterhuis, Trijntje met Richie, Lionel
- Oot n' Oots, The
- Ooyy (Henrik Olsson, Swedish composer and producer)
- Ooze (Swedish ambient producer Sebastian Mullaert)
- Ooze, Ivan
- Oozes, The
- OP8 (Giant Sand/Lisa Germano collaboration)
- OP8 feat. Germano, Lisa
- Opaali
- Opac (French psych-folk band from Tours (One-man project : Pierre-Alexis Cottereau, but performing in band))
- Opal (80s US alternative rock band)
- Opal In Sky
- Opał (Polish MC)
- Opania, Marian
- Opanije
- Opatovský, Robo
- Opaz
- Opća opasnost
- OPcrotte
- Opeia, Cazzi
- Opel, Billy
- Opel, Jackie
- Open
- Open Air Stereo
- OPEN ARMS (UK Pop Band)
- Open Circle, The
- Open City (Punk Hardcore)
- Open Door
- Open Fifth
- Open Hand (American indie rock band)
- Open Mike Eagle (US rapper and comedian)
- Open Mike Eagle & White, Paul
- Open Mike Eagle feat. Alpha MC
- 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
