- O
- OO
- OO
- OO
- OO
- OOak
- OakObe
- ObeObl
- OblOC
- OCOce
- OceOck
- OckOct
- OctOdd
- OddOde
- OdeODO
- odoOer
- OerOff
- OffOff
- OffOgi
- OgiOh
- OhOhh
- OhiOin
- OinOK
- OKokg
- okgOl
- OlOLB
- OlcOld
- OldOle
- OleOli
- OliOli
- OliOll
- OllOls
- OlsOma
- OmaOMC
- OmdOmi
- Omkon
- OnOnc
- OncOne
- OneOne
- OneOne
- OneOnh
- ONIOnl
- onl
- Oon
- OONOpe
- OpeOph
- OphOpt
- OptOra
- OraOrb
- ORBOrc
- OrcOrc
- OrcOre
- OreOrg
- OrgOri
- OriOri
- Oriorm
- OrnOrp
- OrpOrq
- OrqOrt
- OrtOsa
- OsaOsc
- OscOsk
- oskOss
- OssOT
- OtaOth
- Othott
- OTTOtt
- OttOur
- OurOut
- OutOut
- OutOut
- OutOva
- OvaOve
- OveOvi
- OviOwe
- OweOx
- OXOyi
- Ozi
- oziOZZ
- Open Mike Eagle feat. Nocando & Barman, Paul, MC
- Open Mike Eagle feat. Serengeti
- Open Mike Eagle feat. Toy Light
- Open Mike Eagle feat. Video Dave and Still Rift
- Open Mike Eagle feat.Brown, Danny
- Open Mind, The (68–73 UK psychedelic rock band)
- Open Minded
- Open Palms
- Open Road (US bluegrass group)
- Open Sails
- Open Sea, The
- Open Season (Australian RAC band)
- Open Sky
- Open Skyz
- Open the Door for Three
- Open the Skies
- Open Trench
- Open University, The
- Open Up and Bleeds, The
- Open, The
- OpenBSD
- Openside
- Opensight (Metal)
- Opensouls
- Opera (Polish group)
- Opera (Italian hard trance project)
- Opera Alaska
- Opera Australia
- Opéra Bastille, Orchestre de l’, Chung, Myung-Whun
- Opera Chaotique
- Opéra de Nuit
- Opera Diabolicus (Doom/Black/Death Metal Swedish Band)
- Opera Familia
- Opera IX
- Opera Magna
- Opera Magna feat. Marta Barbé
- Opera Multi Steel
- OperaBabes
- Operación Triunfo (fake artist)
- Operación Triunfo 2009
- Operación Triunfo 2017
- Operación Triunfo 2018
- Operación Triunfo 2023
- Operación Triunfo 2025 (OT Series 13)
- Operación Triunfo, Academia
- Operaciya Plastilin
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operating Tracks, The
- Operating Tracks, The feat. Anitchka, Emma
- Operating Tracks, The feat. Rein
- Operation
- Operation Cunt Destroyer (Scottish slam/brutal death metal/deathcore)
- Operation Ivy
- Operation M.D, The
- Operation Mindcrime
- Operation Ratification
- Operation Semtex
- Operation Sodasteal (kaj strife & slaney(in)famous)
- Operation Winter Mist
- Opération Zéro
- Operation, The
- Operation, The (predecessor to mewithoutYou)
- Operator (Hard Rock Band)
- Operator Please
- Operator, Hello
- Operators (Canadian band)
- Operators, The (US indie rock band, Emily Arkin/Jen Godfrey/Paul Coleman)
- Operators, The (British indie rock band)
- Operators, The (ska, from Indianapolis, IN)
- Operazioni
- Operelly
- Operus
- Opeth (Swedish progressive metal/rock)
- OPFuture (German rapper)
- OPFuture & 4tune
- OPFuture & Niname
- OPFuture & Voodoo Beats
- OPFuture, Parker & Freakso
- OPFuture, Shwabadi & Charizma867
- Opgeduveld
- Opgekonkerd
- Opgezwolle (Dutch rap group)
- Opgezwolle feat. Vrieling, Bert
- Ophanin
- Ophelia Ragtime Orchestra
- Ophelia's Eye (Melodic death metal band from Switzerland)
- Opheliac
- Ophelias, The (psychedelic rock band from San Francisco)
- Ophelias, The (Cincinnati indie rock band)
