- O
- OO
- OO
- OOak
- OakObe
- ObeObs
- ObsOce
- OceOct
- OctOdd
- OddODE
- ODEODV
- OdyOff
- OffOG
- OGOH
- OHOhm
- OhmOjo
- OjoOki
- Oki
- Old
- OldOle
- OleOli
- OliOlr
- OlsOMA
- OmaOme
- Omeon
- OnONE
- OneONE
- ONEOne
- oneOnl
- OnlOnw
- OnwOpa
- OpaOph
- OphOr
- OrOrb
- OrbOrc
- OrcOre
- OreOri
- OriOrk
- OrkOrp
- OrpOrs
- OrsOs
- OsOsc
- OscOsl
- OsmOsu
- OsuOtn
- OtoOtt
- OttOur
- OurOut
- OutOut
- OutOve
- OveOvi
- OviOwe
- OweOxo
- Oxo
- OZZ
- O’G3NE (formerly “Lisa, Amy & Shelley”)
- O’Halloran, Dustin
- O’Halloran, Dustin & Gyða Valtýsdóttir
- O’Halloran, Dustin & Senti, Bryan
- O’Halloran, Dustin & Siggi String Quartet
- O’Halloran, Dustin, ACME String Quartet
- O’Hara, Catherine
- O’Hara, Jamie
- O’Hara, Jill
- O’Hara, Kelli
- O’Hara, Kelli, Pasquale, Steven & Company
- O’Hara, Mary (Irish soprano and harpist)
- O’Hara, Mary Margaret
- O’Hara, Paige, White, Richard and Chorus
- O’Hearn, Patrick (American bass guitarist and keyboardist)
- O’Hora, Ronan, Royal Philharmonic Orchestra, Carney, Jonathan
- O’Jays, The
- O’Kanes, The
- O’Kaysions, The
- O’Keefe Music Foundation (Music School)
- O’Keefe, Danny
- O’Keefe, Johnny
- O’Keefe, Laurence & Benjamin, Nell
- O’Malley, Katie
- O’Meara, Jo
- O’My’s, The (Chicago rock/soul duo)
- O’Neal, Alexander
- O’Neal, Alexander feat. Cherrelle
- O’Neal, Shaquille (performs as DJ Diesel aka Diesel)
- O’Neal, Shaquille feat. RZA & Method Man
- O’Neil, Melissa
- O’Neill, Lisa (Irish singer)
- O’Neill, Sharon
- O’Neill, Terry (Irish balladeer, "A Nation Once Again" among others)
- O’Quin, Greg
- O’Reilly, Emmett (Respire)
- O’Reilly, Kevan
- O’Reilly, Marty & the Old Soul Orchestra (acoustic folk/blues band)
- O’Reillys and the Paddyhats, The
- O’Riley, Christopher (American pianist)
- O’Rion, Alex
- O’Riordan, Dolores
- O’Rourke, Declan
- O’Rourke, Jim (US musician & producer)
- O’Shaughnessy, Ryan (Irish singer-songwriter and former actor)
- O’Shine, Simon & Navel, Adam
- O’Shine, Simon & Romel, Ahmed
- O’Sullivan, Daniel (British multi‐instrumentalist and composer)
- O’Sullivan, Gilbert
- O’Sullivan, Gilbert & Lee, Peggy
- O’Sullivan, Gilbert Feat. Hucknall, Mick
- O’Sullivan, Gilbert Feat. Tunstall, KT
- O’Toole, Rich
- O+S
- O5 & Radeček
- Oaf1
- OAFF
- OAG
- Oai Star
- Oaio
- Oak (French post-rock band)
- Oak (Swedish Hardcore, Screamo)
- Oak Pantheon (American atmospheric black metal band)
- Oak Ridge Boys, The
- Oak, Ken
- Oak, Meghan
- Oak, Nadia
- Oak, Northern
- Oak, Pete
- Oak, Winona
- Oakahtoakseh (Finnish experimental folk & spoken word group)
- Oakdale Drive
- Oakenfold, Paul
- Oakenfold, Paul & Disfunktion feat. Spitfire
- Oakenfold, Paul & Fonsi, Luis
- Oakenfold, Paul & Fox, Cassandra
- Oakenfold, Paul & Goss, Matt
- Oakenfold, Paul & Suckley, Jordan
- Oakenfold, Paul and Amoeba Assassin
- Oakenfold, Paul and Young, Christopher
- Oakenfold, Paul feat. Amoeba Assassin
- Oakenfold, Paul feat. Asher D
- Oakenfold, Paul feat. Bisnow, Austin
- Oakenfold, Paul feat. Furtado, Nelly & Tricky
- Oakenfold, Paul feat. Goss, Matt
- Oakenfold, Paul feat. Ice Cube
- Oakenfold, Paul feat. Infected Mushroom
- Oakenfold, Paul feat. Keenan, Tamra
- Oakenfold, Paul feat. Lacey, Tiff
- Oakenfold, Paul feat. Lacey, Tiff
