- O
- OO
- OO
- OOak
- OakObe
- ObeObs
- ObsOce
- OceOct
- OctOdd
- OddODE
- ODEOdu
- ODVOff
- OffOG
- OGOh
- OHOhm
- OhmOjo
- OjoOki
- OkiOla
- OlaOld
- OldOle
- OleOli
- OliOlo
- OloOma
- OmaOme
- OmeON
- ONOne
- OneONE
- ONEOne
- OneOnl
- OnlOnu
- OnwOpa
- OpaOph
- OphOR
- OrOrb
- OrbOrc
- OrcOre
- OreOri
- OriOrk
- OrkOrp
- OrpOrs
- Orsory
- OrzOsc
- OscOsl
- OslOst
- OstOti
- OtiOtt
- OttOur
- OurOut
- OutOut
- OutOve
- OveOve
- OveOwe
- OweOxm
- OXOOzo
- OzoOZZ
- Ó (Formerly Eskimeaux)
- O (Olivier Marguerit)
- O (Black metal/Grindcore from Italy)
- Ö (Nicolas Petitfrère, aka Nömak)
- o Bardo e o Banjo (Brazilian bluegrass band)
- Õ C'EST NOUS
- o Cantador, Santanna
- Ó Ceannabháin, Eoghan (Irish folk musician)
- O Conqueror
- Ó do Forró
- O Emperor (five-piece rock band from Waterford, Ireland)
- O Grilo
- O Inimigo
- O Karaiva
- Ö la Palöma Boys
- Ô Lake
- O Linea
- Ó Lionáird, Iarla
- O Melhor de MPB
- O Mer
- Ô Paon
- O Pioneers!!!
- O Positive
- O Safari (synth pop duo from Rennes)
- O Samuli A
- O Satânico Dr. Mao e os Espiões Secretos (Brazilian Punk Band)
- O Simbolo
- O Terno
- O Verme Vencedor
- o Visitante, Luiz
- O-Hum (Iranian band)
- O-Shen
- O-Zone (Moldovan eurodance pop group)
- O-Zone Percussion Group, The
- O‐Town
- O, Ashley (fictional pop star from Black Mirror TV series)
- O, Bobby
- O, Karen
- O, Karen & Danger Mouse
- O, Karen and Kids, The
- O, Karen with Reznor, Trent and Ross, Atticus
- O, Olivia (American solo performances by Olivia Osby)
- O, Rodney
- O, Rodney & Cooley, Joe
- O, The
- O!Kult
- O. (Tash Keary & Joe Henwood)
- O. Cas
- O. Children
- O., Jenny
- O., Jens
- O.A.R.
- O.B.F.
- O.B.F. feat. Belén Natalí
- O.B.F. feat. Charlie P
- O.B.F. feat. Williamz, Mr.
- O.C. (East-Coast US rapper Omar Credle)
- O.C. & Organized Konfusion
- O.C. feat. Beman, Nick
- O.C. feat. Chubb Rock & Jeru the Damaja
- O.C. feat. Organized Konfusion
- O.C. Supertones, The
- O.C.A.D (Olivia Cipolla and Arie Dixon)
- O.Children
- O.F.T.B. (Watts hip-hop group)
- O.G. (rapper)
- O.G. (German rapper)
- O.G. Black
- O.G. Black feat. Voltio
- O.G. feat. Nimo
- O.G. Pezo
- O.G. Pezo & Lucio101
- O.G. Pezo, LockeNumma19 & Mista Meta
- O.G.C. (US hardcore rap group Originoo Gunn Clappaz)
- O.L.I.V.I.A. (Argentinian experimental pop music)
- O.M.G.
- o.n.a.
- O.O.D.
- O.P.KING
- O.R.k.
- O.R.k. feat. Tankian, Serj
- O.R.O. (Italian pop)
- O.S., Arun (Carnatic Vocalist)
- O.S.T.R. (Polish rapper, musician and producer)
- O.S.T.R. & Hades
- O.S.T.R. & Hades (Duo of two polish rappers)
- O.S.T.R. & Marco Polo
- O.S.T.R. & Sofa
- O.S.T.R. feat. El da Sensei
- O.S.T.R. feat. Green
