- Omnimar
- Omnimotion
- Omnioid
- Omnis (ambient / drone)
- Omnisoul
- Omnispawn
- Omnitica
- Omnitron (Thrash Metal band from Sweden)
- Omnium Gatherum
- Omnivortex
- Omnyama, Mfaz'
- Omodaka
- 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
- OMP
- Omp El Capitán (Dominican Christian music singer)
- Omri
- Oms, Kuba
- Omul cu Șobolani
- Omulu + King Dou Dou
- OMY, The
- ON (Sylvain Chauveau and Steven Hess with rotating guest artists)
- On (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 Inc.
- On My Honor
- 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-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 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
