- O
- OO
- OO
- OOak
- OakOb
- ObeOBO
- ObrOce
- OceOch
- Och
- OctODE
- OdeODO
- odoOf
- OfOff
- OffOgr
- OgrOh
- OhaOis
- OisOka
- OkaOku
- OkuOlc
- OldOld
- OldOli
- OliOli
- OliOls
- OlsOma
- OmaOme
- OMFOn
- OnOne
- OneOne
- ONEOne
- oneOnk
- OnkOnT
- OntOor
- OorOpe
- OpeOpu
- OpuOra
- OraOrc
- OrcOrd
- OrdOrh
- OrhOri
- OriOrl
- OrlOrq
- OrqOrt
- OrtOsa
- OsaOsc
- OscOsm
- Osn
- Otr
- OtrOtt
- OttOur
- OurOut
- OutOut
- OutOve
- OveOve
- OveOwe
- OweOxi
- OxiOze
- ozz
- 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
- Opalo
- 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 (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. 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
