- O
- OO
- OO
- OO
- OOak
- OakObe
- ObeObr
- ObrOcc
- OccOce
- OceOct
- OctOdd
- OddODE
- ODEOdp
- OdrOfa
- OFBOff
- OffOge
- OgeOh
- OhOhm
- OhmOje
- OjeOKA
- OKAOku
- OkuOla
- OLAOld
- OldOle
- OleOli
- OliOli
- OliOls
- OlsOma
- OmaOme
- OmeOmo
- OmoOnc
- OncOne
- OneOne
- OneOne
- OneONL
- ONLOno
- OnoOok
- OokOpe
- OpeOpi
- OpiOQu
- OquOra
- oraOrb
- orbOrc
- OrcOre
- OreOri
- ORIOri
- OriOrl
- OrlOrp
- OrpOrr
- OrrOrt
- ortOsb
- OsbOsc
- OscOsm
- OsmOst
- OstOth
- OthOtt
- OttOty
- OtyOur
- OurOut
- OutOut
- OutOv
- OvOve
- OveOvn
- OvnOwe
- OweOxi
- Oxl
- OZZ
- OZZozz
- Omoinotake
- Omonoko (Northern Irish Alt pop quartet)
- Omophagia (Death Metal from Zurich)
- OMORI (Composers of the video game soundtrack “Omori”)
- Omori, Aki
- Omori, Cullen
- Omori, Hinako
- Ōmori, Toshiyuki
- Omosumo
- Omoto, Trevor & UNDY
- 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 Doudou
- OMY, The
- ON (Sylvain Chauveau and Steven Hess with rotating guest artists)
- ON (solo project of Ken Andrews)
- ON (Spanish metal band)
- 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 and Ons, The
- 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 Man feat. Falola, Femi
- On My Honor
- On Planets
- On Planets & Flaws
- On Prend L'Air
- On Regret
- On Solid Ground
- On the Floor (German gothic rock band from Hamburg)
- On the House
- 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 Rise
- 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 Trial
- On Video
- On Wave (indie)
- On-lyne (Warframe fictional boy band)
- ON-OFF (AC/DC cover band from northern Italy)
- On-The-Go
- ON! (aka Tequila & the Sunrise Gang) (German punk-rock band)
- ON/OFF (Japanese Band)
- Ona Mae
- Ona Nua
- Onabule, Ola
- ONAIR
- Önal, Ayşe Hatun
- Önal, Füsun
- Onar (Polish MC)
- Onar gościnnie Lerek
- Onarsé
- Onasis, Ariez
- Onasis, Ariez feat. Cossom, Kevin
- Onasis, Erick
- Oñate, Jorge
- Oñate, Jorge & López, Álvaro
- 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 Grace Forever
