| Title | Publisher | Year | Language | Documents |
|---|---|---|---|---|
| Outsided | Chad Elliott | 1999 | English | Solution |
| Over Here! | Lionel Ange |
2020 | English | Solution, Map, Hints |
| Overdog | Mega-Soft | 1989 | English | Solution |
| Overheard! | Grim Reaper, The |
1992 | English | |
| Overlord | Elise C. Boucher (Zosia the Pious) |
1986 | English | Solution |
| Owl Consults, The | Cidney Hamilton, Nick Mathewson, Thomas Mack | 2017 | English | |
| Oxbridge | Tynesoft | 1986 | English | Solution, Hints |
| Oxphar | ERE Informatique | 1987 | French | Solution |
| Oxygen | Benjamin Sokal | 2010 | English | Solution |
| Oxygen | Hansi Berlin | 2015 | English |