| Obituary | : | Slowly We Rot | goden | |
| Obitus | : | Coupe De Grace | lorjef | |
| Obscure Devotion | : | Son Of A Dayless Night | j. mcintyre | |
| Obscurity | : | Damnation's Pride | brand | |
| Obsecration | : | The Inheritors Of Pain | sharund | |
| Obskurum | : | The Ceremony And The Descent | grymyrk | |
| Obtained Enslavement | : | Centuries Of Sorrow | brand | |
| Obtained Enslavement | : | Witchcraft | blackgoat | |
| Obtest | : | Tukstantmetis | boris | |
| Occultus | : | Cosmos | brand | |
| Octinomos | : | On The Demiurge | bathym | |
| Odes Of Ecstasy | : | Atheistic Emotions | j. mcintyre | |
| Officium Triste | : | Ne Vivam | sharund | |
| Of The Fallen | : | Ancient Gods Of Battles Past | lord vic | |
| Of The Fallen | : | Ancient Gods Of Battles Past | skullcrusher | |
| Old Forest | : | Into The Old Forest | lord pesten | |
| Old Funeral | : | Join The Funeral Procession | lord pesten | |
| Old Funeral | : | The Older Ones | j. mcintyre | |
| Old Funeral | : | The Older Ones | lord vic | |
| Old Mans Child | : | Born Of The Flickering | sauron anarazel | |
| Old Mans Child | : | Revelation 666 | wrath | |
| Old Wainds | : | Zdes' Nikogda Ne Shodyat Snega... | boris | |
| Omen | : | Battle Cry | ramrod | |
| One Last Sin | : | One Last Sin | skullcrusher | |
| Onslaught | : | Power From Hell | chorazaim | |
| Ontoson | : | Somber Chaotic Entrance... | orodruin | |
| Opera Ix | : | The Black Opera | boris | |
| Opera Ix | : | The Black Opera | dwaallicht | |
| Opera Ix | : | The Black Opera | w.s. diabolus | |
| Opera Ix | : | The Call Of The Wood | brand | |
| Opera Ix | : | Sacro Culto | boris | |
| Opera Ix | : | Sacro Culto | brand | |
| Operation Winter Mist | : | Rehearsal Demo | grymyrk | |
| Operation Winter Mist | : | Winter Warfare | grymyrk | |
| Opeth | : | Blackwater Park | daoloth | |
| Opeth | : | Damnation | skullcrusher | |
| Opeth | : | Morningrise | raagoonshinnaah | |
| Opeth | : | Morningrise | sauron anarazel | |
| Opeth | : | My Arms, Your Hearse | blackgoat | |
| Opeth | : | My Arms, Your Hearse | the barrow man | |
| Opeth | : | Orchid | boris | |
| Opeth | : | Still Life | c. drishner | |
| Opeth | : | Still Life | raagoonshinnaah | |
| Ophthalamia | : | To Elishia | malphas | |
| Opus Malefici | : | Obscure Thoughts | brand | |
| Orange Goblin | : | The Big Black | malphas | |
| Orange Goblin | : | Time Travelling Blues | malphas | |
| Orcustus | : | Demo 2002 | skullcrusher | |
| Order From Chaos | : | An Ending In Fire | sharund | |
| Order From Chaos | : | Dawnbringer | brand | |
| Order From Chaos | : | Stillbirth Machine | grotesque | |
| Ordo Equilibrio | : | Reaping The Fallen...The First Harvest | bathym | |
| Ork | : | Through The Fight, I Ride | boris | |
| Orkus | : | The Gate | equimanthorn | |
| Osbourne, Ozzy | : | Bark At The Moon | sharund | |
| Osbourne, Ozzy | : | The Ozzman Cometh | mlotek | |
| Osculum Infame | : | The Black Theology | herr nebelwerfer | |
| Osculum Infame | : | Dor-Nu-Fauglith | black hate | |
| Osculum Infame | : | Dor-Nu-Fauglith | brand | |
| Osculum Infame | : | Dor-Nu-Fauglith | herr nebelwerfer | |
| Osculum Infame | : | Dor-Nu-Fauglith | lord pesten | |
| Ossuary | : | We Await The Secret Conspiracy | brand | |
| Otyg | : | Alvefard | chorazaim | |
| Ouroboros | : | Invoking The Worm | hando | |
| Oxiplegatz | : | Sidereal Journey | c. drishner | |
| Oxiplegatz | : | Sidereal Journey | j. mcintyre | |
| Oyhra | : | Na Yazichnitzkai Zyamli | boris | |
| Oyhra | : | Ratnaya Strala | boris |