| name | games | status | region | founded | closed | activity | |
|---|
| O-Games |
20 | | | | | 2006/2012 | |
| O&K Pasokon Kyoushitsu |
14 | | | | | 1983/1984 | |
| O2 Games |
2 | | | | | 2014/2015 | |
| O3 Entertainment |
5 | | | | | 2004/2007 | |
| Oak Corp |
2 | | | | | 1982/1983 | |
| Oak Software |
2 | dead | UK | 1983 | 1984 | 1983/1984 | |
| Oase Software |
2 | dead | DE | 1990 | 1996 | 1990/1992 | |
| Oasis Games |
6 | | | | | 2016/2019 | |
| Oasis Software |
10 | | | | | 1983/1992 | |
| Oberon Games |
3 | | | | | 2004/2006 | |
| Oberon Media |
24 | | | | | 1995/2010 | |
| Object Software |
3 | | | | | 2001/2002 | |
| Object Vision Software |
1 | | | | | 2011/2011 | |
| Obsidian Entertainment |
37 | active | US | 2003 | | 2004/2019 | http://www.obsidianent.com/ |
| Obunsha |
6 | | | | | 1997/1998 | |
| Ocean Media |
28 | | | | | 2010/2024 | |
| Ocean |
820 | name changed | UK | 1983 | 1998 | 1983/1999 | Founded as Spectrum Games in 1983, but renamed soon into Ocean. Infogrames UK since … |
| Oceanside Interactive |
3 | | | | | 2010/2011 | |
| Octagon |
3 | | | | | 1995/1996 | |
| Octaspire |
6 | | | | | | |
| Octave |
2 | | | | | 2004/2004 | |
| Octopi |
2 | | | | | 2006/2006 | |
| Oddlabs |
5 | | | | | 2005/2009 | |
| Oddworld Inhabitants |
20 | dead | US | 1994 | | 1997/2020 | Oddworld Inhabitants Inc. Founders: Sherry McKenna, Lorne Lanning HQ: San Luis … |
| Odesta |
10 | | | | | 1982/1984 | |
| Odin |
18 | | | | | 1985/1988 | |
| Odisea Software |
3 | dead | ES | 1988 | 1988 | 1988/1988 | |
| Odyssey Software |
5 | dead | US | | | 1990/2008 | Developed games for 2 different unlicensed NES publishers in the USA. |
| OeFun |
5 | | | | | 2006/2014 | |
| Off the Wall Productions |
4 | | | 1990 | 1991 | 1990/1991 | |
| Office Create |
10 | | | | | 1994/2017 | |
| Office Koukan |
4 | | JP | | | 1990/1991 | |
| Offset Software |
3 | dead | US | 2004 | 2010 | 2010/2010 | HQ: Newport Beach, California Founders: Sam McGrath, Travis Stringer, Trevor Stringer … |
| Oh, a Rock! Studios |
5 | | | | | 2012/2017 | |
| OHBA-Do |
4 | | | | | 2002/2002 | |
| Ohio Scientific |
52 | bought | US | 1975 | 1981 | 1977/1981 | Ohio Scientific, Inc. Ohio Scientific Instruments, Ohio Scientific of Puerto Rico … |
| Oiko Entertainment |
| | FRA | | | | |
| Okado |
3 | | | | | 1983/1984 | |
| Old School Games |
6 | active | | | | 2013/2013 | |
| OlderGames |
12 | | | | | 2002/2007 | |
| Olympia |
5 | | ITA | | | 1979/1983 | |
| OMC Games |
2 | | | | | 1999/1999 | |
| Omega Force |
89 | active | JP | 1996 | | 1998/2021 | Division of Koei Tecmo. |
| Omega Micott |
5 | | | | | 2000/2002 | |
| Omega Software |
10 | dead | UK | 1983 | 1985 | 1983/1984 | |
| Omega-Soft |
2 | | | | | 1983/1983 | |
| Omegavision |
3 | | | | | 1990/1990 | |
| Omen Software |
6 | | UK | | | 1983/1984 | |
| Omiod |
6 | | IT | | | 1993/2014 | |
| Omiya Soft |
8 | | | | | 1996/2016 | |
