- O
- OO
- OO
- OO
- OOAF
- OAFOak
- OakObe
- ObeObo
- OboOca
- OcaOce
- OceOct
- OctOct
- OCTOdd
- OddODE
- ODEOdu
- Oduof
- OfOff
- OffOfM
- OfnOgu
- OOh
- OhOho
- OHoOje
- OjeOKA
- OKAOkt
- OkuOla
- OlaOld
- OldOle
- OleOli
- OliOli
- OliOll
- OllOls
- OlsOma
- OmaOme
- OmeOmm
- OmnOn
- OnOnd
- OndOne
- OneOne
- OneOne
- OneOni
- OniOnl
- onlOny
- OnyOos
- OotOpe
- OpeOpp
- OppOr
- OrOra
- oraOrb
- OrbOrc
- OrcOrd
- OrdOrg
- OrgOri
- OriOri
- OriOrl
- OrlOrp
- OrpOrq
- OrqOrt
- OrtOsa
- OsaOsc
- OscOsk
- OskOss
- OssOta
- Oti
- OtiOtt
- Ott
- Our
- OurOut
- OutOut
- OutOut
- OutOve
- OveOve
- OveOwe
- OWEOwl
- OwlOxm
- oXnOzc
- OzcOzu
- Ozuozz
- 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 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)
- Ophidian (hardcore dj)
- Ophidian & Minckz
- 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
- Opio (Opion Lindsey - US rapper, from Souls of Mischief)
- Opio del Mono
- Opiom
- Opitz, Barbi
- Opium (Belgian all girl pop group)
- Opium du Peuple
- Opium Jukebox
- Opium Moon
- Opium Owl (heavy psych rock band from Riga, Latvia)
- OPIUM project (Russian electronic group)
- Opium Warlords
- Opiuo (Australian electronica / breakbeat artist)
- Opiuo feat. Gift of Gab & Syreneiscreamy
- opius dei oficial
- OPLIAM
- OPM (1999–current US dub pop hip‐hop punk reggae group)
- OPM & Big B
- OPM feat. Dirtball, The & Big B
- Opodebota
- Opolopo & Johnson, Angela
- Opossom (New Zealand)
- OPP
- Oppenheimer
- Oppenheimer Analysis
- Oppenheimer, Andy (member of Oppenheimer Analysis)
- Oppera
- Oppermann, Rüdiger
- Oppidan
