| Game Name | System |
|---|
| Organiser II LZ64S | MAME |
| Organiser II P200 | MAME |
| Organiser II P350 | MAME |
| Organiser II P464 | MAME |
| Organiser II XP | MAME |
| Oric 1 | MAME |
| Oric Atmos | MAME |
| Oric Telestrat | MAME |
| Orient Gardens (19xx)(-)(It) | ZX Spectrum (TAP) |
| Orient Gardens (19xx)(-)(It) | ZX Spectrum Z80 |
| Orient Gardens (19xx)(-)(It)[a] | ZX Spectrum (TAP) |
| Orient Quest (E)(G)(PUSSYCAT) | NDS |
| Oriental Beauty (10213511, NSW/ACT) | MAME |
| Oriental Blue - Ao no Tengai (J)(Cezar) | GBA |
| Oriental Diamonds (Barcrest) (German) (MPU4) | MAME |
| Oriental Games | Amiga |
| Oriental Games (1990)(Micro Style)(Disk 1 of 2) | Atari ST |
| Oriental Games (1990)(Micro Style)(Disk 1 of 2)[cr Delight] | Atari ST |
| Oriental Games (1990)(Micro Style)(Disk 1 of 2)[protected] | Atari ST |
| Oriental Games (1990)(Micro Style)(Disk 2 of 2) | Atari ST |
| Oriental Games (1990)(Micro Style)(Disk 2 of 2)[cr Delight] | Atari ST |
| Oriental Games (1990)(Micro Style)(Disk 2 of 2)[protected] | Atari ST |
| Oriental Games (UK) (1990) | CPC |
| Oriental Hero (1987)(Firebird) | ZX Spectrum Z80 |
| Oriental Hero (1987)(Firebird)[a] | ZX Spectrum Z80 |
| Oriental Legend / Xi You Shi E Zhuan (ver. 105, Korean Board) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 111, Chinese Board) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 111, Korean Board) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 111, Taiwanese Board) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 112) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 112, Chinese Board) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. 126) | MAME |
| Oriental Legend / Xi You Shi E Zhuan (ver. ???, Chinese Board) | MAME |
| Oriental Legend 2 (V101, China) | MAME |
| Oriental Legend 2 (V103, China) | MAME |
| Oriental Legend 2 (V104, China) | MAME |
| Oriental Legend Special / Xi You Shi E Zhuan Super (ver. 100, set 1) | MAME |
| Oriental Legend Special / Xi You Shi E Zhuan Super (ver. 100, set 2) | MAME |
| Oriental Legend Special / Xi You Shi E Zhuan Super (ver. 101, Korean Board) | MAME |
| Oriental Legend Special / Xi You Shi E Zhuan Super (ver. 103, China, Tencent) (unprotected) | MAME |
| Oriental Legend Special Plus / Xi You Shi E Zhuan Super Plus | MAME |
| Orifice from Outer Space, The (UK) (19xx) | CPC |
| Origami (CD-i) | CD-I |
| Origamo (1994)(Destiny Software Productions) | DOS |
| Original Atari ST Cheat Disk v1.3r, The (1990)(K.M.E.) | Atari ST |
| Original Frisbee Disc Sports - Ultimate & Golf (E)(sUppLeX) | NDS |
| Original Frisbee Disc Sports - Ultimate & Golf (U)(EXiMiUS) | NDS |
| Original Games (2001)(Tau Software) | X68K |
| Original Moorhuhn Jagd, Die (Germany) | GBC |
| Original Story from Fairy Tail - Gekitotsu! Kardia Daiseidou (J) | NDS |
| Original, The (demo-playable) (1994-05-13)(Meyer, Gerrit)(en-de)(SW) | Atari ST |
| Orion (1983)(Software Projects) | ZX Spectrum (TAP) |
| Orion (1983)(Software Projects) | ZX Spectrum Z80 |
| Orion (1983)(Software Projects)[a] | ZX Spectrum Z80 |
| Orion (E) | C64 Tapes |
| Orion (S) (19xx) | CPC |
| Orion 128 | MAME |
| Orion 128 (MS7007) | MAME |
| Orion 128 + Z80 Card II | MAME |
| Orion 128 + Z80 Card II (MS7007) | MAME |
| Orion 128 + Z80 Card II + IDE | MAME |
| Orion 128 + Z80 Card II + IDE (MS7007) | MAME |
| Orion Comspiracy CD, The (1995)(Domark) | DOS |
| Orion Conspiracy (1995)(Domark)(F) | DOS |
| Orion Pro | MAME |
| Orion Project (1994)(Joel Strawn) | DOS |
| Orion' Run v0.7c (demo-playable) (19xx)(Beery'sBit Software)(PD) | Atari ST |
| Orius (ver UAA) | MAME |
| Orizon-Micro | MAME |
| Ork | Amiga |
| Ork (1991)(Psygnosis)(Disk 1 of 2)[cr MCA][t] | Atari ST |
| Ork (1991)(Psygnosis)(Disk 1 of 2)[cr MCA][t][a] | Atari ST |
| Ork (1991)(Psygnosis)(Disk 2 of 2)[cr MCA][t] | Atari ST |
| Orlando Magic (Bwb) (MPU4) (set 1) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 2) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 3) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 4) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 5) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 6) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 7) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 8) | MAME |
| Orlando Magic (Bwb) (MPU4) (set 9) | MAME |
| Ormuz (S) (1988) | CPC |
| Orphee (F) (1985) (Disk 1 of 2) | CPC |
| Orphee (F) (1985) (Disk 1 of 2) [a1] | CPC |
| Orphee (F) (1985) (Disk 1 of 2) [a2] | CPC |
| Orphee (F) (1985) (Disk 2 of 2) | CPC |
| Orphee (F) (1985) (Disk 2 of 2) [a1] | CPC |
| Orphee (F) (1985) [h1] | CPC |
| Orphen - Scion of Sorcery (Europe) | PS2 |
| Orphen - Scion of Sorcery (USA) | PS2 |
| Orpheus and the Underword (1985)(A&F)[ORPHEUS start] [SSD] | BBC Micro |
| Orpheus and the Underword (1985)(A&F)[a2][ORPHEUS start] [SSD] | BBC Micro |
| Orpheus and the Underword (1985)(A&F)[a][ORPHEUS start] [SSD] | BBC Micro |
| Orpheus and the Underword (1985)(A&F)[h TSTH][bootfile] [SSD] | BBC Micro |
| Orson | Atari 800 |
| Orstalon, The (1992)(Mark Evans)(128k)[Unfinished] | ZX Spectrum Z80 |
| Ortho Repere (F) (19xx) | CPC |
| Ortho Repere (F) (19xx) [a1] | CPC |
| Orthocrack_1 | Atari 800 |
