Oni Red Chords

France

Onion Hardcore

unknown

Onion Mind Game Records

USA

Oniric Records

Spain

Onirik Circle

France

Onism Productions

United-Kingdom

Only 4 Stars Record

France

Only Much Louder Records

India

Only Rock

unknown

Only Vinyl Is Real

France

Onlyhate Productions

Brazil

Onlyhate Propaganda

Brazil

Onlypops Records

unknown

ONN

unknown

Onodrim Production

France

ONR (Obscure NWOBHM Releases)

Greece

Onset Audio

unknown

Onslaught Of Steel

USA

Onslaught Records

Mexico

Onslow Records

Germany

ONSP

unknown

Onward Music

United-Kingdom

Onyxia

Finland

Oolossi Records

Ukraine

Oomoxx Media

unknown

Opa Loka Records

Germany

Opaco Records

Italy

Opale Records

unknown

Opaqus Records

USA

Opción Sónica

Mexico

Open All Night Records

unknown

Open Beats

unknown

Open Coffin Records

unknown

Open E Music

USA

Open Eye Records

USA

Open Grave Productions

Chile

Open Grave Records

USA

Open Media

Czechia

Open Metal Records

France

Open Mind Records

unknown

Open Music

unknown

Open Records

USA

Open Sea Records

unknown

Open The Road

Brazil

Open Up Music

unknown

Open Wound Records

USA

Open Your Ears Music

Ireland

Open Your Eyes Fanzine

Germany

Open Your Eyes Records

USA

Operator Produkzion

Russia

Ophiucus Records

USA

Opinionate Records

Sweden

OPM Records

USA

OPN Records

France

Opoponax Records

USA

Oppahappa Records

Sweden

Opposing Music

Russia

Opposite Productions

France

Opposite Records

Iran

Oppress Records

unknown

Oppressive Sound System Releases

USA

Öpstone Productions

Finland

Optical Records

unknown

Optimum

unknown

Optimus Discos

Portugal

Opus

Czechia

Opus 3

unknown

Opus Dei's Licence Productions

Switzerland

Opus Magnum Productions

Netherlands

Opus Records

USA

Ora Serrata

unknown

Oracle Distribution Service

Australia

Oracle Netlabel

Chile

Oracle Records (AUS)

Australia

Oracle Records (UK)

United-Kingdom

Oral Diarrhoea Records

Russia

Oral Records

Canada

Orange Recordings

USA

Orange Records

Canada

OrangeHaus Empire

Germany

Orate Asusta A Turistas Con Motosierra Records

Chile

Oration

Iceland

Oratorivm Records

Chile

Orb Weaver

unknown

Orbit

unknown

Orbovoid Records

Netherlands

ORC Production

unknown

Orca Records

Germany

Orca Wolf Records

USA

Orchestrated Dystopia Records

United-Kingdom

Orchestrated Misery Recordings

USA

Orchestrated Records

USA

Orchidscent

France

Orcinus Records

unknown

Orcrist

unknown

Orcynia Records

France

Orda Et Terram Tenebrae

unknown

Ordealis Records

France

Ordem Negra Productions

Brazil

Order Noktondurner

Russia