| Game Name | System |
|---|
| One On One (1983)(Electronic Arts) | ZX Spectrum (TAP) |
| One On One (1983)(Electronic Arts)[cr] | Apple2 |
| One On One Basketball | 7800 |
| One Piece - Gear Spirit (J)(Caravan) | NDS |
| One Piece - Gear Spirit (K)(Coolpoint) | NDS |
| One Piece - Gigant Battle (E) | NDS |
| One Piece - Gigant Battle (F) | NDS |
| One Piece - Gigant Battle (G) | NDS |
| One Piece - Gigant Battle (J) | NDS |
| One Piece - Going Baseball Haejeok Yaku (K)(Independent) | GBA |
| One Piece - Grand Battle 3 (NTSC-J) | GCN |
| One Piece - Grand Battle Swan Colloseum (J) | WSC |
| One Piece - Mansion (USA) | PSX2PSP |
| One Piece - Mansion [NTSC-U] | PSX |
| One Piece - Mezase! King of Paris (J)(Cezar) | GBA |
| One Piece - Nanatsu Shima no Daihihou (J)(Cezar) | GBA |
| One Piece - Round the Land! (Europe) (De,Es,It) | PS2 |
| One Piece Dragon Dream (J)(Caravan) | GBA |
| One Piece Gigant Battle 2 - Shin Sekai (J) | NDS |
| One Piece Going Baseball (J)(Eurasia) | GBA |
| One Piece Grand Adventure | GCN |
| One Piece Grand Battle | GCN |
| One Piece Mansion (E) | PSX |
| One Piece Mansion (Japan) | PSX |
| One Piece Pirates Carnival | GCN |
| One Queen Puzzle, The (19xx)(CSSCGC) | ZX Spectrum Z80 |
| One Shot One Kill | MAME |
| One Step Beyond (1993)(Ocean) | DOS |
| One [NTSC-U] | PSX |
| One for the Road (1985)(Analog)[k-file] | Atari 800 |
| One on One (1983)(Electronic Arts)[k-file] | Atari 800 |
| One on One (E) | C64 Tapes |
| One on One (Japan) (Demo) | PSX |
| One on One (UE) | C64 PP |
| One on One (UE) [alt] | C64 PP |
| One's Plasma Factory (F) (2000) (PD) | CPC |
| OneChanbara Special (Japan) | PSP |
| One_Moon_and_Two_Suns | Atari 800 |
| One_on_One_Compute! | Atari 800 |
| Onegai Monsters (Japan) | N64 |
| Onegai My Melody - Yume no Kuni no Daibouken (J)(WRG) | NDS |
| Onesimus A Quest for Freedom (1993)(Ark Multimedia) | DOS |
| Ongaku Tkool 3 (Japan) | PSX |
| Ongaku Tsukuru Kanaderu (Japan) | SNES |
| Oni (Europe) | PS2 |
| Oni (France) | PS2 |
| Oni (Germany) | PS2 |
| Oni (USA) | PS2 |
| Oni - The Ninja Master (Japan) | MAME |
| Oni II - Innin Densetsu (Japan) | GB |
| Oni III - Kuro no Hakaishin (Japan) | GB |
| Oni IV - Kijin no Ketsuzoku (Japan) | GB |
| Oni V - Innin o Tsugumono (Japan) | GB |
| Oni Zero - Sengoku Ransei Hyakkaryouran (J)(6rz) | NDS |
| Onigashima Pachinkoten (Japan) | GB |
| Onimusha (Japan) | PS2 |
| Onimusha - Blade Warriors (Europe) (En,Fr,De) | PS2 |
| Onimusha - Blade Warriors (USA) | PS2 |
| Onimusha - Dawn of Dreams (Europe) (En,Fr,De,Es,It) (Disc 1) | PS2 |
| Onimusha - Dawn of Dreams (Europe) (En,Fr,De,Es,It) (Disc 2) | PS2 |
| Onimusha - Dawn of Dreams (USA) (En,Ja) (Disc 1) | PS2 |
| Onimusha - Dawn of Dreams (USA) (En,Ja) (Disc 2) | PS2 |
| Onimusha - Warlords (Europe) (En,Fr,De) | PS2 |
| Onimusha - Warlords (USA) (En,Ja) | PS2 |
| Onimusha 2 (Japan) (SLPM-65100) | PS2 |
| Onimusha 2 (Japan) (SLPM-65101) | PS2 |
| Onimusha 2 - Samurai's Destiny (Europe) (En,Fr,De,Es,It) | PS2 |
| Onimusha 2 - Samurai's Destiny (USA) | PS2 |
| Onimusha 3 (Japan) | PS2 |
| Onimusha 3 - Demon Siege (Europe, Australia) (En,Fr,De,Es,It) | PS2 |
| Onimusha 3 - Demon Siege (USA) | PS2 |
| Onimusha Tactics (E)(Patience) | GBA |
| Onimusha Tactics (J)(Eurasia) | GBA |
| Onimusha Tactics (U)(Mode7) | GBA |
| Onizuka Katsuya Super Virtual Boxing - Shin Kentou Ou Densetsu (Japan) | SNES |
| Online Backgammon (1991)(Becker, David)(FW)[Monochrome] | Atari ST |
| Online Chess Kingdoms (Europe) | PSP |
| Online Chess Kingdoms (USA) | PSP |
| Online World Handbook, The v1.7 (19xx)(-)[h 8-Bit](TBI-80-1)[bootfile] [SSD] | BBC Micro |
| Online World Handbook, The v1.7 (19xx)(-)[h 8-Bit](TBI-80-2)[bootfile] [SSD] | BBC Micro |
| Online World Handbook, The v1.7 (19xx)(-)[h 8-Bit](TBI-80-3)[bootfile] [SSD] | BBC Micro |
| Only Fools & Horses (Bellfruit) (set 1) (Scorpion 2/3) | MAME |
| Only Fools & Horses (Bellfruit) (set 2) (Scorpion 2/3) | MAME |
| Only Fools & Horses (Bellfruit) (set 3) (Scorpion 2/3) | MAME |
| Only Fools & Horses (Bellfruit) (set 4) (Scorpion 2/3) | MAME |
| Only Fools & Horses (Bellfruit) (set 5) (Scorpion 2/3) | MAME |
| Only Fools and Horses (Bellfruit) (Scorpion 1?) | MAME |
| Only For Your Eyes II Megademo (UK) (1995) (PD) (Disk 1 of 2) | CPC |
| Only For Your Eyes II Megademo (UK) (1995) (PD) (Disk 2 of 2) | CPC |
| Only! Valency (1994-12-06)(Schulz, Jens)(de)(SW) | Atari ST |
| Onmyou Taisenki Zeroshiki (J)(Caravan) | GBA |
| Onna Sansirou - Typhoon Gal (set 1) | MAME |
| Onna Sansirou - Typhoon Gal (set 2) | MAME |
| Onore no Shinzuru Michi wo Yuke (Japan) | PSP |
| Onsei Kanjou Sokuteiki - Kokoro Scan (J)(Loli) | NDS |
| Onslaught | Amiga |
| Onslaught (1982)(H. Lentchner)[k-file] | Atari 800 |
| Onslaught (1989)(Realms) | Atari ST |
| Onslaught (1989)(Realms)[cr Equinox][t] | Atari ST |
| Onslaught (1989)(Realms)[cr Equinox][t][a] | Atari ST |
