- O
- OO
- OO
- OOak
- OakObe
- ObeObs
- ObsOce
- OceOCS
- OCSOda
- OdaODE
- ODEODU
- ODUOfe
- OfeOfr
- oftOh
- OhOhj
- OHKOji
- OJMOke
- OkeOla
- OlaOld
- OldOle
- OleOli
- OliOll
- OllOm
- OmOme
- OmeOmn
- OmnOnc
- One
- OneOne
- OneOni
- ONIOno
- OnoOon
- OonOpe
- OpeOpt
- Ora
- OraOrc
- OrcOrd
- OrdOrg
- OrhOri
- OriOrm
- OrmOrq
- OrqOrt
- OrtOsb
- OsbOsh
- OshOss
- OssOTF
- OtgOtt
- OttOue
- OueOut
- OutOut
- OutOut
- OutOve
- OveOwe
- OweOwn
- OwsOza
- OzaOZZ
- Omnivide
- Omnivortex
- OMNOM (Tech House artist)
- Omnyama, Mfaz'
- Omodaka
- Omodaka (Soichi Terada)
- OMOH (Pop electro french duo)
- Omoinotake
- Omonoko (Northern Irish Alt pop quartet)
- OMORI (Composers of the video game soundtrack “Omori”)
- Omori, Cullen
- Omori, Hinako
- Ōmori, Toshiyuki
- Omosumo
- Omotola
- OMP
- Omp El Capitán (Dominican Christian music singer)
- OMR (French Rapper)
- Omri (emo electro)
- Oms, Kuba (Canadian soul singer and producer)
- Omul cu Șobolani
- Omulu + King Dou Dou
- OMY, The
- ON (Sylvain Chauveau and Steven Hess with rotating guest artists)
- ON (solo project of Ken Andrews)
- ON (Hardcore)
- on a créé un monstre
- On a Dead Machine
- On a Friday (pre‐Radiohead group, until 1991)
- On a Hiding to Nothing
- ON AN ON
- On Atlas’ Shoulders
- On Being an Angel
- On Being Human
- On Broken Wings
- On Call Heroes
- On Camera
- On Dead Waves
- On Holiday (Oklahoma City ska punk)
- On Inc.
- On Man
- On My Honor
- On Planets & Flaws
- On Regret
- On Solid Ground
- On the Last Day
- On the Line All-Stars, The
- On the Loose (doom metal band from Portugal)
- On the Might of Princes
- On the Rocks (all male a cappella group from the University of Oregon)
- On Thorns I Lay (death/doom/gothic metal band from Greece)
- On Thorns I Lay (French Doom Metal Band)
- On Tonight
- On Video
- On Wave (indie)
- On-lyne (Warframe fictional boy band)
- ON-OFF (AC/DC cover band from northern Italy)
- On-The-Go
- ON/OFF (Japanese Band)
- Ona Nua
- ONAIR
- Önal, Ayşe Hatun
- Önal, Füsun
- Onar (Polish MC)
- Onarsé
- Onasis, Ariez
- Onasis, Ariez feat. Cossom, Kevin
- Onasis, Erick
- Oñate, Jorge
- Onay, Gülsin
- ONBC (Danish indie rock)
- Onbeskaamd (Afrikaans worship music project group based in South Africa)
- Once (Germany)
- Once a Pawn
- Once a Tree
- Once Again (Dancefloor project by Michael Schendel, active in the mid 1990s)
- Once and Future Band
- Once Blue
- Once Dead (Heavy Metal from L.A.)
- Once Human
- Once Human feat. Flynn, Robert
- Once Human, Flynn, Robert
- Once Monsters (UK Band)
- Once Never Again (Belgian late 1990s hardcore band)
- Once Nothing
- Once Tiros
- Once Upon a Dead Man
- Once Upon a Time (lead Bruno Adams)
- Once upon a winter
- Once, The
