- O
- OO
- OO
- OO
- OO
- OOak
- OakObe
- ObeOBL
- OblObs
- Obsoce
- OceOce
- oceOct
- OctOda
- OdbOdd
- OddOde
- OdeODU
- ODUOf
- OfOff
- OFFOfi
- Ofiogo
- OGROh
- OhOhi
- OhiOIL
- OilOk
- OkOke
- OkeOl
- OlOla
- OlaOld
- OldOl
- OlOlg
- OlgOli
- OliOli
- OliOls
- OlsOMA
- OmaOma
- OmaOme
- OmeOmn
- OmnOn
- OnOne
- ONEOne
- OneOne
- OneOne
- OneONJ
- OnkOnn
- ONOOny
- OnyOos
- OosOpe
- OpOpi
- OpiOpu
- OpuOra
- Oraorb
- OrbOrc
- OrcOrc
- OrcOre
- OreOrh
- OrhOri
- ORIOrk
- OrkOrn
- OrnOrq
- OrqOrr
- OrrOrt
- OrtOsa
- OsaOsc
- OscOsk
- OskOss
- OssOT
- OtaOth
- OthOtt
- OttOtt
- OttOur
- OurOut
- OutOut
- OutOut
- OutOv
- OvOve
- OveOve
- OveOwe
- OweOwl
- OwlOxl
- Oxl
- OzaOzo
- OzoOzz
- Opéra Bastille, Orchestre de l’, Chung, Myung-Whun
- Opera Chaotique
- 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
- Operador
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operatic
- Operatika (symphonic metal)
- Operating Theatre
- Operating Tracks, The
- Operating Tracks, The feat. Anitchka, Emma
- Operating Tracks, The feat. Rein
- Operation Cunt Destroyer (Scottish slam/brutal death metal/deathcore)
- Operation Ivy
- Operation M.D, The
- Operation Mindcrime
- Operation Semtex
- Operation Sodasteal (kaj strife & slaney(in)famous)
- Operation Winter Mist
- Opération Zéro
- Operation, The
- Operation, The (predecessor to mewithoutYou)
- Operation: Cliff Clavin
- 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
- Opgekonkerd & Vieze Asbak
- 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)
- Ophidian (hardcore dj)
- Ophidian & Minckz
- Ophidian & Peacock, Dr.
- Ophidian & Playah, Tha
- Ophidian Ascension, The (Australian death metal)
- Ophidian I
- Ophidian Memory
- Ophis (Germany, Metal)
- Ophthalamia
- Opi the Hit Machine
- Opia (indie electronic group: Cole Citrenbaum, DJ Stanfill and colorthought)
- Opia (Western Australian band)
- Opiate for the Masses
- Opick
- Opin (Richmond, VA experimental electronic)
- Opio (Opion Lindsey - US rapper, from Souls of Mischief)
- Opio del Mono
- Opiom
- Opitz, Barbi
- Opium Jukebox
- Opium Moon
- Opium Owl (heavy psych rock band from Riga, Latvia)
- OPIUM project (Russian electronic group)
- Opium Tea
- Opium Warlords
