- O
- OO
- OO
- OOak
- OakObe
- ObeObr
- ObrOce
- OceOch
- OchOct
- OctOde
- Odeodo
- OdoOf
- OfOff
- OffOgr
- OgrOha
- OhaOis
- OisOka
- OkaOku
- OkuOld
- OldOld
- OldOli
- OliOli
- OliOls
- OlsOma
- OmaOMF
- OMFOn
- OnOne
- OneONE
- ONEone
- OneOnk
- ONLOnt
- ontOor
- OOpe
- OpeOpu
- OpuOra
- OraOrc
- OrcOrd
- OrdOrh
- OrhOri
- OriOrl
- OrlOrq
- OrqOrt
- OrtOsa
- OsaOsc
- Oscoso
- OsoOta
- OtaOtr
- OtrOtt
- OttOur
- OurOut
- OutOut
- OutOve
- Oveovg
- OviOwe
- OweOxi
- Oxi
- ozz
- 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)
- Onar gościnnie Lerek
- 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
- Öncel, Nazan
- OnCue
- Ond Cirkel
- Onda (Michaelangelo L'Acqua & Gregg Fine)
- Onda Sabanera
- Onda Vaga
- Onda Vaga & Serrano, Jorge
- Onda Vaselina
- Onda, Carlo
- Onda, Naoyuki
- Ondara, J.S.
- Ondas Marteles, Las
- Ondatrópica
- Önder (Dutch-Turkish rapper Önder Doğan)
- Onderadio
- Ondina (eurodance vocalist)
- Ondra, Jakub (Czech vocalist, guitarist and songwriter)
- Ondrasik, John
- Ondreaz
- Ondřej Havelka a jeho Melody Makers
- Ondskapt (Swedish black metal)
- Ondt Blod (Norwegian hardcore punk band)
- OnDubGround
- OnDubGround feat. Brother Culture
- One (Greek/Cypriot pop boyband)
- One (Florida hard rock band, affiliated with Sevendust)
- One (Canadian reggae group)
- One (UK rap crew, w/ members Sway, Pyrelli, etc.)
