| Title | Publisher | Year | Language | Documents |
|---|---|---|---|---|
| Obscure Naturalist, The | Peter Hague | 1990 | English | |
| Ogre | Richard Hunt | ? | English | |
| Oklib's Revenge | Syntax Adventure Magazine | 1992 | English | |
| Old Castle, The | Silly Software | ? | English | |
| Once a King | Darryn Lavery |
1988 | English | Solution |
| Oo-topos | Penguin Software |
1981 | English | Solution |
| Ooze - Als die Geister Murbe Wurden | Ariolasoft, Dragonware | 1988 | German | Solution |
| Ooze: Creepy Nites | Dragonware | 1989 | English | Solution |
| Opaline | Interactive Technology |
1990 | English | |
| Operation Blue Sunrise | Colin Campbell |
1990 | English | |
| Operation Hongkong | Golden Games | 1986 | German | Solution |