| artist,genre,country | |
| O'BROTHER,Post Rock/Math rock,United States | |
| DAV 'LIST,Crossover Prog,United Kingdom | |
| GAVI 'LOGHLEN & COTTERS BEQUEST,Prog Folk,Australia | |
| Ô-LIOSTÉRE,Jazz Rock/Fusion,France | |
| O-U,RIO/Avant-Prog,Japan | |
| O.L.D.,Experimental/Post Metal,United States | |
| O.R.K.,Progressive Metal,United Kingdom | |
| OAK,Crossover Prog,Norway | |
| OAKSENHAM,Symphonic Prog,Armenia | |
| OAQK,Post Rock/Math rock,Japan | |
| OATS,Psychedelic/Space Rock,United States | |
| FRÉDÉRIC D BERLAND,Progressive Electronic,France | |
| OBERON,Crossover Prog,Italy | |
| OBERON,Prog Folk,United Kingdom | |
| OBIYMY DOSCHU,Crossover Prog,Ukraine | |
| OBLIGOD / EX FOX TERRITORY,Post Rock/Math rock,Czech Republic | |
| OBLIQUE RAIN,Progressive Metal,Portugal | |
| OBLIVION SUN,Eclectic Prog,United States | |
| OBLOMOV,Tech/Extreme Prog Metal,Czech Republic | |
| OBSCURA,Rock Progressivo Italiano,Italy | |
| OBSCURA,Tech/Extreme Prog Metal,Germany | |
| OBSIDIAN,Tech/Extreme Prog Metal,Netherlands | |
| OBSIDIAN KINGDOM,Experimental/Post Metal,Spain | |
| OBSIDIAN MANTRA,Tech/Extreme Prog Metal,Poland | |
| OBSIDIAN TIDE,Tech/Extreme Prog Metal,Israel | |
| OBSIDIAN TONGUE,Experimental/Post Metal,United States | |
| OBSKURIA,Psychedelic/Space Rock,Multi-National | |
| OBSKYR,Eclectic Prog,Sweden | |
| OBSTACLES,Post Rock/Math rock,Denmark | |
| OC FEEF,Psychedelic/Space Rock,United States | |
| OCARINAH,Canterbury Scene,France | |
| OCEAN,Neo-Prog,Norway | |
| OCEAN,Symphonic Prog,Germany | |
| OCEAN,Heavy Prog,France | |
| OCEAN ARCHITECTURE,Progressive Metal,United States | |
| TH CEAN DOESN'T WANT ME,Experimental/Post Metal,South Africa | |
| OCEAN'S EDGE,Progressive Metal,Greece | |
| TH CEAN,Experimental/Post Metal,Germany | |
| OCEANA COMPANY,Heavy Prog,Netherlands | |
| OCEANBORN,Progressive Metal,United States | |
| OCEANIC,Post Rock/Math rock,Canada | |
| OCEANIC,Progressive Metal,Israel | |
| OCEANICA,Progressive Metal,United Kingdom | |
| OCEANS 5,Crossover Prog,United Kingdom | |
| OCEANS OF NIGHT,Progressive Metal,United States | |
| OCEANS OF SADNESS,Tech/Extreme Prog Metal,Belgium | |
| OCEANS OF SLUMBER,Tech/Extreme Prog Metal,United States | |
| OCEANSIZE,Psychedelic/Space Rock,United Kingdom | |
| OCH,Krautrock,Sweden | |
| OCHRE,Progressive Metal,Australia | |
| OCNOS,Crossover Prog,Spain | |
| OCOAI,Experimental/Post Metal,United States | |
| OCRILIM,Tech/Extreme Prog Metal,United States | |
| OCTAFISH,RIO/Avant-Prog,Germany | |
| OCTARINE SKY,Crossover Prog,United States | |
| OCTAVIO SENDERO,Psychedelic/Space Rock,Argentina | |
| OCTAVISION,Progressive Metal,United States | |
| OCTAVO,RIO/Avant-Prog,France | |
| OCTILLIAN,Progressive Metal,Canada | |
| OCTOBER,Jazz Rock/Fusion,United States | |
| OCTOBER EQUUS,RIO/Avant-Prog,Spain | |
| OCTOBER PROJECT,Prog Folk,United States | |
| OCTOBRE,Crossover Prog,Canada | |
| OCTOHPERA,Eclectic Prog,Brazil | |
| OCTOPIE,Crossover Prog,Finland | |
| OCTOPUS,Progressive Metal,Chile | |
| OCTOPUS,Psychedelic/Space Rock,United Kingdom | |
| OCTOPUS,Psychedelic/Space Rock,Germany | |
| OCTOPUS (NOR),Symphonic Prog,Norway | |
| OCTOPUS RIDE,Psychedelic/Space Rock,Sweden | |
| OCTOPUS SYNG,Psychedelic/Space Rock,Finland | |
| ODD DIMENSION,Progressive Metal,Italy | |
| ODD FICTION,Tech/Extreme Prog Metal,France | |
| ODD JOHN HAWKINS,Eclectic Prog,Puerto Rico | |
| ODD LOGIC,Progressive Metal,United States | |
| ODD PALACE,Heavy Prog,Denmark | |
| ODDARRANG,Post Rock/Math rock,Finland | |
| ODDLAND,Progressive Metal,Finland | |
| ODDTOMATIC,Crossover Prog,Finland | |
| ODE AND ELEGY,Experimental/Post Metal,United States | |
| TH DEJA,Rock Progressivo Italiano,Italy | |
| ODEM ARCARUM,Tech/Extreme Prog Metal,Germany | |
| ODESSA,Crossover Prog,Italy | |
| ODILE,Crossover Prog,Germany | |
| ODIN,Heavy Prog,United Kingdom | |
| ODIN'S COURT,Progressive Metal,United States | |
| ODISSEA,Rock Progressivo Italiano,Italy | |
| ROMA DOJ,Crossover Prog,Poland | |
| ODRADEK ROOM,Experimental/Post Metal,Ukraine | |
| ODRAREG,Jazz Rock/Fusion,Venezuela | |
| ODRAZA,Experimental/Post Metal,Poland | |
| ODYSSEE,Eclectic Prog,Germany | |
| ODYSSEY,Progressive Metal,Sweden | |
| ODYSSEY,Progressive Metal,United States | |
| ODYSSICE,Symphonic Prog,Netherlands | |
| L EIL DU SOURD,Jazz Rock/Fusion,France | |
| OF SOUND MIND,Crossover Prog,Canada | |
| OF THE I,Heavy Prog,Switzerland | |
| OF WONDROUS LEGENDS (O.W.L.),Prog Folk,United States | |
| OFFA REX,Prog Folk,Various | |
| OFFENBACH,Prog Related,Canada | |
| OFFERING,Zeuhl,France | |
| OFFICINA MECCANICA,Rock Progressivo Italiano,Italy | |
| OG MUSIQUE,Crossover Prog,Belgium | |
| OGIVES,RIO/Avant-Prog,Belgium | |
| OGLIN,Crossover Prog,Sweden | |
| OGO DYS,Eclectic Prog,Sweden | |
| OGRÓD WYOBRAźNI,Crossover Prog,Poland | |
| BARTOS GRODOWICZ,Crossover Prog,Poland | |
| OH HIROSHIMA,Post Rock/Math rock,Sweden | |
| OH NO ONO,Crossover Prog,Denmark | |
| OH.,Crossover Prog,Greece | |
| OHEAD,Psychedelic/Space Rock,United Kingdom | |
| OHGOD!,Experimental/Post Metal,South Africa | |
| OHM,Jazz Rock/Fusion,United States | |
| OHMPHREY,Jazz Rock/Fusion,United States | |
| OHO,RIO/Avant-Prog,United States | |
| OIAPOK,Jazz Rock/Fusion,France | |
| OINGO BOINGO,Crossover Prog,United States | |
| OISEAUX - TEMPETE,Post Rock/Math rock,France | |
| OK GOODNIGHT,Progressive Metal,United States | |
| OKETO,Post Rock/Math rock,United States | |
| OKO,Heavy Prog,Yugoslavia | |
| OKTA LOGUE,Psychedelic/Space Rock,Germany | |
| OKTOBER,Krautrock,Germany | |
| OKTOPUS,Heavy Prog,United Kingdom | |
| RY KUMOTO,Eclectic Prog,Japan | |
| OKYR,Progressive Metal,Brazil | |
| TH LD DEAD TREE,Experimental/Post Metal,France | |
| TH LD MAN & THE SEA,Crossover Prog,Denmark | |
| OLD MAN GLOOM,Experimental/Post Metal,United States | |
| TH LD MILL FREE ENSEMBLE,Psychedelic/Space Rock,Italy | |
| OLD ROCK CITY ORCHESTRA,Crossover Prog,Italy | |
| OLD TIME RELIJUN,RIO/Avant-Prog,United States | |
| MIK LDFIELD,Crossover Prog,United Kingdom | |
| SALL LDFIELD,Crossover Prog,Ireland | |
| OLE LUKKOYE,Psychedelic/Space Rock,Russia | |
| OLIVE MESS,RIO/Avant-Prog,Latvia | |
| OLIVER,Crossover Prog,United Kingdom | |
| OLLOCS,Heavy Prog,United States | |
| OLOFERNE,Prog Folk,Italy | |
| OM ART FORMATION,Prog Related,Bulgaria | |
| OMB,Experimental/Post Metal,Israel | |
| L MBRA DELLA SERA,Rock Progressivo Italiano,Italy | |
| OMBRALUCE,Rock Progressivo Italiano,Italy | |
| OMEGA,Psychedelic/Space Rock,Hungary | |
| TH MEGA EXPERIMENT,Experimental/Post Metal,United States | |
| OMEGA MASSIF,Experimental/Post Metal,Germany | |
| OMENOPUS,Psychedelic/Space Rock,United Kingdom | |
| OMERTAH,Experimental/Post Metal,Ukraine | |
| OMESTHESIA,Psychedelic/Space Rock,Spain | |
| OMIE WISE,Eclectic Prog,Portugal | |
| OMIT,Progressive Electronic,New Zealand | |
| OMNEROD,Tech/Extreme Prog Metal,Belgium | |
| OMNI,Prog Folk,Spain | |
| OMNIA,Symphonic Prog,Argentina | |
| OMNIA OPERA,Psychedelic/Space Rock,United Kingdom | |
| OMNIBEING,Progressive Metal,Belarus | |
| TH MNIFIC,Progressive Metal,Australia | |
| OMNIPOTENT YOUTH SOCIETY,Eclectic Prog,China | |
| OMNIPRESENT,Crossover Prog,United States | |
| OMNISIGHT,Progressive Metal,United States | |
| OMOIDE HATOBA,Krautrock,Japan | |
| ON THE RAW,Jazz Rock/Fusion,Spain | |
| ONCE AND FUTURE BAND,Crossover Prog,United States | |
| ONCE THEM EDENS,Tech/Extreme Prog Metal,Greece | |
| ONE,Symphonic Prog,Argentina | |
| ONE OF THESE DAYS & THEE HEAVY RANDOM TONE COLOUR LAB,Psychedelic/Space Rock,Spain | |
| ONE SHOT,Jazz Rock/Fusion,France | |
| ONE STARVING DAY,Experimental/Post Metal,Italy | |
| ONE STEP FROM THE EDGE,Tech/Extreme Prog Metal,Greece | |
| ONE SWITCH TO COLLISION,Psychedelic/Space Rock,Multi-National | |
| ONEIDA,Psychedelic/Space Rock,United States | |
| TH NEIRA,Crossover Prog,Multi-National | |
| ONEIRONAUGHT,Progressive Metal,United States | |
| ONEOHTRIX POINT NEVER,Progressive Electronic,United States | |
| ONEVOICE,Crossover Prog,United States | |
| ONGKARA,Crossover Prog,Russia | |
| ONGO,Progressive Metal,Puerto Rico | |
| ONIRIC,Crossover Prog,Italy | |
| ONIRIC PROJECT,Crossover Prog,Italy | |
| ONIRIS,Symphonic Prog,France | |
| TH NIRIST,Neo-Prog,France | |
| RYOK NO,Zeuhl,Japan | |
| ONSÉGEN ENSEMBLE,Heavy Prog,Finland | |
| ÁNGE NTALVA,Jazz Rock/Fusion,Spain | |
| ONTOFIELD,Crossover Prog,United Kingdom | |
| ONTOGENY,Tech/Extreme Prog Metal,United States | |
| ONYOU,Krautrock,United States | |
| ONYRIC JOY,Psychedelic/Space Rock,Spain | |
| ONYSUS,Progressive Metal,Portugal | |
| ONYX EYES,Progressive Metal,Germany | |
| ONZA,Neo-Prog,Spain | |
| OOIOO,RIO/Avant-Prog,Japan | |
| ÖOOOOOOOOOO,Experimental/Post Metal,France | |
| OÖPHOI,Progressive Electronic,Italy | |
| OORT,Neo-Prog,France | |
| OORT SMOG,RIO/Avant-Prog,United States | |
| OPA,Jazz Rock/Fusion,Uruguay | |
| OPABINIA,RIO/Avant-Prog,Japan | |
| OPALE,Crossover Prog,France | |
| OPEN AIR,Crossover Prog,France | |
| OPEN EYE BAND,Prog Folk,Finland | |
| TH PEN WINDOW,Eclectic Prog,United States | |
| OPENSIGHT,Progressive Metal,Colombia | |
| OPENSPACE,Progressive Metal,Poland | |
| OPERA OSCURA,Progressive Metal,Italy | |
| OPERATION: MILKSNATCH,Eclectic Prog,United States | |
| OPETH,Tech/Extreme Prog Metal,Sweden | |
| OPHICINA,Rock Progressivo Italiano,Italy | |
| OPHIUCUS,Crossover Prog,France | |
| TH PIUM CARTEL,Crossover Prog,Norway | |
| OPOSSUM,Jazz Rock/Fusion,Germany | |
| OPPOSING MOTION,Progressive Metal,United Kingdom | |
| OPPOSITE EARTH,Progressive Metal,United States | |
| TH PPOSITE OF HATE,Progressive Metal,Brazil | |
| OPRA MEDITERRANEA,Rock Progressivo Italiano,Italy | |
| OPRAM,Heavy Prog,France | |
| OPTICAL*8,RIO/Avant-Prog,Japan | |
| OPUS,Symphonic Prog,Yugoslavia | |
| OPUS 3,Heavy Prog,Chile | |
| OPUS AVANTRA,RIO/Avant-Prog,Italy | |
| OPUS DÄI,Progressive Metal,United States | |
| OPUS EST,Neo-Prog,Sweden | |
| OPUS OF A MACHINE,Progressive Metal,Australia | |
| OPUS SYMBIOSIS,Crossover Prog,Finland | |
| OPUS TIDE,Progressive Metal,United Kingdom | |
| OPUS V,Progressive Metal,Brazil | |
| OPUS-5,Jazz Rock/Fusion,Canada | |
| OPUSCULUS,Heavy Prog,Canada | |
| ORA NOMBRO,Progressive Metal,Italy | |
| THE RACLE MACHINE,Progressive Metal,Germany | |
| ORAKLE,Tech/Extreme Prog Metal,France | |
| ORANGE CLOCKS,Psychedelic/Space Rock,United Kingdom | |
| ORANGE PEEL,Krautrock,Germany | |
| ORANGE SHADING STARLIGHT,Psychedelic/Space Rock,Italy | |
| ORANGE TULIP CONSPIRACY,RIO/Avant-Prog,United States | |
| ORANSSI PAZUZU,Experimental/Post Metal,Finland | |
| ORANZADA,Psychedelic/Space Rock,Poland | |
| ORATRISM,Heavy Prog,France | |
| ORBS,Crossover Prog,United States | |
| ORCHESTRA NJERVUDAROV,RIO/Avant-Prog,Italy | |
| ORCHESTRA OF THE UPPER ATMOSPHERE,RIO/Avant-Prog,United Kingdom | |
| ORCHESTRA PANICA,Crossover Prog,Italy | |
| ORCHESTRE CELESTI,Crossover Prog,Italy | |
| L RCHESTRE SYMPATHIQUE,Jazz Rock/Fusion,Canada | |
| ORDER OF THE LIVING,Eclectic Prog,Finland | |
| TH RDINAIRES,RIO/Avant-Prog,United States | |
| ORDINARY BRAINWASH,Crossover Prog,Poland | |
| ORDO DRACONIS,Experimental/Post Metal,Netherlands | |
| OREGON,Jazz Rock/Fusion,United States | |
| LA REJAS Y LA LENGUA,RIO/Avant-Prog,Argentina | |
| ORENDA,Progressive Metal,France | |
| ŘRESUND SPACE COLLECTIVE,Psychedelic/Space Rock,Multi-National | |
| ORFANADO,Prog Folk,Italy | |
| MARTI RFORD,Neo-Prog,United Kingdom | |
| ORGAN:,Experimental/Post Metal,Norway | |
| ORGANIC IS ORGASMIC,Psychedelic/Space Rock,Russia | |
| ORGANIC NOISES,Jazz Rock/Fusion,Poland | |
| ORGANIC REACTION,Progressive Metal,Brazil | |
| ORGANISATION,Krautrock,Germany | |
| ORGANIZED CHAOS,Progressive Metal,Serbia | |
| ORGIYA PRAVEDNIKOV,Eclectic Prog,Russia | |
| ORGONE,Tech/Extreme Prog Metal,United States | |
| L RIENT D'Ô,Symphonic Prog,Canada | |
| TH RIENT EXPRESS,Indo-Prog/Raga Rock,Multi-National | |
| ORIENT SQUEEZERS,Indo-Prog/Raga Rock,Sweden | |
| ORIENTAL SUNSHINE,Indo-Prog/Raga Rock,Multi-National | |
| ORIGENS,Heavy Prog,Brazil | |
| ORIGINS,Eclectic Prog,United States | |
| ORION,Symphonic Prog,France | |
| ORION,Crossover Prog,Georgia | |
| ORION DUST,Heavy Prog,France | |
| ORION TANGO,Psychedelic/Space Rock,United States | |
| ORION'S BEETHOVEN,Psychedelic/Space Rock,Argentina | |
| ŘRKENKJŘTT,Experimental/Post Metal,Norway | |
| ANDRE RLANDO,Rock Progressivo Italiano,Italy | |
| MICHAE RLANDO,Progressive Metal,United States | |
| L RME,Rock Progressivo Italiano,Italy | |
| ORNE,Eclectic Prog,Finland | |
| ORNITHOS,Rock Progressivo Italiano,Italy | |
| ORPHAN BLOOM,Heavy Prog,United States | |
| ORPHAN PROJECT,Crossover Prog,United States | |
| ORPHANED LAND,Experimental/Post Metal,Israel | |
| ORPHEO,Heavy Prog,Netherlands | |
| ORPHEUS,Crossover Prog,United Kingdom | |
| ORPHEUS,Neo-Prog,Japan | |
| ORPHEUS GHOSTSONG,Prog Folk,United Kingdom | |
| ORPHEUS NINE,Heavy Prog,United States | |
| ORQUESTA METAFÍSICA,RIO/Avant-Prog,Argentina | |
| ORSAK:OSLO,Psychedelic/Space Rock,Sweden | |
| ORTHODOX,Experimental/Post Metal,Spain | |
| TH RTHOTONICS,RIO/Avant-Prog,United States | |
| ORTHRELM,Tech/Extreme Prog Metal,United States | |
| ORVALIANS,Zeuhl,France | |
| ORYZHEIN,Prog Folk,Canada | |
| OS MUNDI,Eclectic Prog,Germany | |
| OSADA VIDA,Heavy Prog,Poland | |
| OSAGE TRIBE,Rock Progressivo Italiano,Italy | |
| OSANNA,Rock Progressivo Italiano,Italy | |
| TH SCILLATION,Psychedelic/Space Rock,United Kingdom | |
| OSCILLAZIONI ALCHEMICO KREATIVE (O.A.K.),Rock Progressivo Italiano,Italy | |
| OSCILLOTRON,Progressive Electronic,Sweden | |
| OSE,Progressive Electronic,France | |
| OSHEAN,Post Rock/Math rock,Russia | |
| OSI,Experimental/Post Metal,United States | |
| OSIBISA,Jazz Rock/Fusion,Ghana | |
| OSIRIS,Neo-Prog,Bahrain | |
| OSIRIS,Tech/Extreme Prog Metal,Netherlands | |
| OSIRIS THE REBIRTH,Psychedelic/Space Rock,United Kingdom | |
| OSJAN / EX OSSIAN,Indo-Prog/Raga Rock,Poland | |
| OSSI DURI,RIO/Avant-Prog,Italy | |
| OSSICLES,Crossover Prog,Norway | |
| OSTA LOVE,Crossover Prog,Germany | |
| OSTINATO,Post Rock/Math rock,United States | |
| MAGNU STRÖM,Jazz Rock/Fusion,Sweden | |
| OSTROVA,Experimental/Post Metal,Spain | |
| OSTURA,Progressive Metal,Lebanon | |
| OT&DO,Crossover Prog,Russia | |
| KIYOMI TAKA,Jazz Rock/Fusion,Japan | |
| OTEME,RIO/Avant-Prog,Italy | |
| TH THELLO SYNDROME,Eclectic Prog,United Kingdom | |
| TH THER SIDE OF THE SKY,Experimental/Post Metal,United States | |
| TH THER SIDE,Neo-Prog,United States | |
| OTHERS BY NO ONE,Tech/Extreme Prog Metal,United States | |
| OTIS GROVE,Jazz Rock/Fusion,United States | |
| OTOLITHEN,RIO/Avant-Prog,Multi-National | |
| OTOMO YOSHIHIDE,RIO/Avant-Prog,Japan | |
| OTOWALA,Jazz Rock/Fusion,United States | |
| L TRACINA,Psychedelic/Space Rock,United States | |
| OTTONE PESANTE,Experimental/Post Metal,Italy | |
| OU,Progressive Metal,China | |
| OUGENWEIDE,Prog Folk,Germany | |
| OULU SPACE JAM COLLECTIVE,Psychedelic/Space Rock,Finland | |
| OUR MAN IN THE BRONZE AGE,Heavy Prog,United Kingdom | |
| OUR OCEANS,Crossover Prog,Netherlands | |
| OUR SOLAR SYSTEM,Krautrock,Sweden | |
| OUT OF FOCUS,Jazz Rock/Fusion,Germany | |
| OUT OF THE BEARDSPACE,Eclectic Prog,United States | |
| OUTCAST,Tech/Extreme Prog Metal,France | |
| OUTER LIMITS,Symphonic Prog,Japan | |
| TH UTERSPACE MILKMEN,Psychedelic/Space Rock,Multi-National | |
| OUTOPSYA,Experimental/Post Metal,Italy | |
| OUTRE MESURE,Jazz Rock/Fusion,France | |
| OUTRUN THE SUNLIGHT,Experimental/Post Metal,United States | |
| OUTSIDE,Neo-Prog,France | |
| OUTSIDE IN,Crossover Prog,New Zealand | |
| OUTWORLD,Progressive Metal,United States | |
| TH VALS,Psychedelic/Space Rock,Australia | |
| OVER THE EARTH,Crossover Prog,France | |
| OVERDRIVE,Neo-Prog,Italy | |
| OVERHEAD,Crossover Prog,Finland | |
| OVERLIFE,Progressive Metal,Spain | |
| OVERLOAD,Neo-Prog,Pakistan | |
| OVERMARS,Experimental/Post Metal,France | |
| OVERTURE,Rock Progressivo Italiano,Italy | |
| OVERWORLD DREAMS,Neo-Prog,United States | |
| OVNI,Neo-Prog,El Salvador | |
| OVRFWRD,Heavy Prog,United States | |
| OVUM,Post Rock/Math rock,Japan | |
| OWANE,Jazz Rock/Fusion,Norway | |
| OWL,Tech/Extreme Prog Metal,Germany | |
| TH WL WATCHES,Jazz Rock/Fusion,United States | |
| OX.EAGLE.LION.MAN,Crossover Prog,United Kingdom | |
| OXES,Post Rock/Math rock,United States | |
| OXHUITZA,Psychedelic/Space Rock,Italy | |
| OXIMORA,Heavy Prog,Mexico | |
| OXIPLEGATZ,Progressive Metal,Sweden | |
| OXOMAXOMA,RIO/Avant-Prog,Mexico | |
| ÖXXÖ XÖÖX,Experimental/Post Metal,France | |
| OYSTERHEAD,Prog Related,United States | |
| OZ URUGULU,Eclectic Prog,Switzerland | |
| OZONE QUARTET,Jazz Rock/Fusion,United States | |
| OZRIC TENTACLES,Psychedelic/Space Rock,United Kingdom | |