- O
- OO
- OO
- OOak
- OakObe
- ObeObs
- ObsOce
- OceOCS
- OCSOda
- OdaODE
- ODEODU
- ODUOfe
- OfeOfr
- oftOh
- OhOhj
- OHKOji
- OJMOke
- OkeOla
- OlaOld
- OldOle
- OleOli
- OliOll
- OllOm
- OmOme
- OmeOmn
- OmnOnc
- One
- OneOne
- OneOni
- ONIOno
- OnoOon
- OonOpe
- OpeOpt
- Ora
- OraOrc
- OrcOrd
- OrdOrg
- OrhOri
- OriOrm
- OrmOrq
- OrqOrt
- OrtOsb
- OsbOsh
- OshOss
- OssOTF
- OtgOtt
- OttOue
- OueOut
- OutOut
- OutOut
- OutOve
- OveOwe
- OweOwn
- OwsOza
- OzaOZZ
- Operación Triunfo 2018
- Operación Triunfo, Academia
- Operaciya Plastilin
- Operadyse (French power metal band)
- Operapop (Operatic pop duo)
- Operatica
- Operatika (symphonic metal)
- Operating Tracks, The
- Operating Tracks, The feat. Rein
- Operation
- Operation Ivy
- Operation M.D, The
- Operation Mindcrime
- Operation Ratification
- Operation Sodasteal (kaj strife & slaney(in)famous)
- Opération Zéro
- Operation, The
- Operator (Hard Rock Band)
- Operator Please
- Operator, Hello
- Operators (Canadian band)
- Operators, The (ska, from Indianapolis, IN)
- Operus
- Opeth (Swedish progressive metal/rock)
- Opgeduveld
- Opgezwolle (Dutch rap group)
- 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 & Peacock, Dr.
- Ophidian & Playah, Tha
- Ophidian I
- Ophidian Memory
- Ophis (Germany, Metal)
- Ophthalamia
- Opi the Hit Machine
- Opia (indie electronic group: Cole Citrenbaum, DJ Stanfill and colorthought)
- Opiate for the Masses
- Opick
- Opio (Opion Lindsey - US rapper, from Souls of Mischief)
- Opio del Mono
- Opium (Belgian all girl pop group)
- Opium du Peuple
- Opium Jukebox
- Opium Moon
- Opium Owl (heavy psych rock band from Riga, Latvia)
- Opium Warlords
- Opiuo (Australian electronica / breakbeat artist)
- Opiuo feat. Gift of Gab & Syreneiscreamy
- OPM (1999–current US dub pop hip‐hop punk reggae group)
- OPM & Big B
- Opodebota
- Opossom (New Zealand)
- OPP
- Oppenheimer
- Oppenheimer Analysis
- Oppenheimer, Andy (member of Oppenheimer Analysis)
- Oppera
- Oppidan
- Oppidan (UK garage producer)
- Opposite The Other
- Opposites, The
- Opposites, The feat. Adje
- Opposites, The feat. Faberyayo & Sjaak
- Opposites, The feat. Hydroboyz & Adje
- Opposites, The feat. Probz, Mr
- Opposites, The feat. Probz, Mr.
- Opposites, The feat. Sef
- Opposites, The feat. Spasmatic
- Opposites, The met Yellow Claw
- Opposition of One
- Opposition, The (London post‐punk band)
- Oppressed, The (Welsh punk/oi)
- Oppressor (US technical death metal)
- Opprobre
- Opprobrium
- OPROER (Belgian indie rock band)
- Opshop
- Opskamatrists, The
- Opsomer, Barbara (Belgian singer)
- Opti-Pop
- Optic
- optic core (experimental electronic/dance producer)
- Optic Sink
- Optiganally Yours
- Optimo (UK techno duo)
