- O
- OO
- OO
- OOak
- OakOb
- ObeObo
- OBOOce
- OceOch
- OchOct
- Odd
- OddODM
- ODOOf
- OfOff
- OFFOgr
- OgrOh
- OhOIR
- OirOKA
- OkaOku
- OkuOla
- OlaOld
- OldOli
- OliOli
- OliOls
- OlsOMA
- OmaOme
- OmeOmo
- OMPOnd
- One
- OneOne
- OneOni
- OniOno
- OnoOom
- OomOpe
- OpeOpp
- OppOra
- OraOrb
- OrbOrc
- OrcOrg
- OrgOri
- OriOrk
- OrkOrp
- OrpOrr
- OrrOrv
- OrvOsb
- OsbOsi
- OsiOst
- OstOth
- OthOtt
- OttOug
- OugOut
- OutOut
- OutOut
- OutOve
- Oveovr
- OVSOwl
- OwlOxy
- Oxy
- ozz
- 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)
- 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 Monsters, Adams, Chloe
- 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
