Region | Title | System | Version | Edition | Languages | Serial | Status |
| Obscure ObsCure | XBOX | | Original | | MI-009 | |
| Obscure ObsCure | PC | 1.1 | Covermount | | | |
| Oddworld: Munch's Oddysee | XBOX | | Original | | MS-001 | |
| Odissea: Sulle tracce di Ulisse (Disc 1) | PC | | Original | | ODY-ITA-P01 | |
| Odissea: Sulle tracce di Ulisse (Disc 2) | PC | | Original | | ODY-ITA-P02 | |
| Offensive Offensive War: The Ultimate Strategical Combat Game | PC | | Covermount | | | |
| Oil Platform Simulator | PC | 1.0 | Original | | | |
| Oil Tycoon 2 Oil Tycoon 2: Il Ritorno di una Leggenda | PC | | EXA Games | | EXAG020 | |
| Olympic Soccer | PC | | CD-ROM Classic Collection 2 | | | |
| Oni | PC | 1.0 | Covermount | | | |
| Only Fun: Entra anche tu nel mondo dei Videogames | PC | | | | | |
| Open Season | XBOX360 | | Original | | US-2024 | |
| Operation: Surgery Has Never Been so Silly! | PC | | Sold Out Software | | | |
| OPSM Best Ever Ever Games Demo | PSX | | Demo | | SCED-02851 | |
| Original War (Disc 1) | PC | 1.02 | Covermount | | | |
| Original War (Disc 1) | PC | 1.02 | Original | | CD-W95-V006-IT1 | |
| Original War (Disc 2) | PC | 1.02 | Covermount | | | |
| Original War (Disc 2) | PC | 1.02 | Original | | CD-W95-V006-IT2 | |
| Oro e Gloria: La Strada per El Dorado | PC | | Covermount | | | |
| Outlaw Golf | PC | | Original | | RM-OUTGOLF-UK | |
| Outpost 2: Divided Destiny | PC | 1.0 | Original | | S0011246 | |
| Over Load | PC | | | | | |
| Overclocked: Una Storia di Violenza | PC | 1.1 | Original | | | |