| Motivetime Ltd. | — | 1 | — |
| Mr Chip Software | 1982 | 1 | — |
| Mucky Foot Productions | 1997 | 1 | — |
| Mythos Games | 1988 | — | — |
| NaturalMotion | October 15, 2001 | 1 | — |
| NDreams | August 2006 | 3 | 4 |
| Nellyvision | — | — | 1 |
| Nerial | — | 8 | — |
| New Star Games | September 19, 2006 | 9 | 2 |
| News of the World | October 1843 | — | 1 |
| NextGenBooks | — | 1 | 1 |
| Nitrome | August 10, 2004 | 2 | 3 |
| No More Robots | — | — | 11 |
| Nomad Games | 2011 | 5 | 6 |
| Nosebleed Interactive | May 29, 2012 | 1 | — |
| Novagen Software | 1984 | 1 | — |
| Nyu Media | 2011 | — | 1 |
| Ocean Software | 1983 | 12 | 23 |
| Orthrus Studios | 2017 | 1 | — |
| Outerlight | December 2002 | 1 | — |
| Outright Games | 2016 | — | 29 |
| Oversight Productions | August 28, 2019 | 1 | — |
| Oxygen Games | 2004 | — | 5 |
| P2 Entertainment | December 23, 2004 | 1 | 1 |
| Palace Software | 1984 | 4 | 1 |
| Panic Barn | August 2012 | 3 | — |
| Perfect Entertainment | 1991 | 3 | — |
| Person of Interests | January 15, 2021 | 1 | 1 |
| Personal Software Services | 1981 | — | 2 |
| Phigames | — | 1 | — |
| Pixel Toys | September 25, 2012 | 1 | 1 |
| Playfish | 2007 | 1 | — |
| Playground Games | 2009 | 5 | — |
| Playsport Games | 2015 | 2 | — |
| Playstack | May 7, 2016 | — | 8 |
| Polygon Treehouse | May 2017 | 1 | — |
| Popcorn Arcade | — | — | 3 |
| Positech Games | 1997 | 5 | 5 |
| PQube | — | — | 34 |
| Proper Games | 2006 | 1 | — |
| Psygnosis | 1984 | 1 | 2 |
| Puppy Games | — | — | 1 |
| Quite Interesting Limited | 1999 | 1 | — |
| Radical Forge | October 13, 2016 | 1 | — |
| Rare Ltd. | 1985 | 45 | 3 |
| Razorback Developments | 2003 | 1 | — |
| Razorworks | 1996 | 1 | — |
| Realtime Worlds | 2002 | 1 | — |
| Rebellion Developments | 1992 | 26 | 10 |
| Red Beard Games | — | 1 | — |
| Red Ego Games | January 20, 2020 | 2 | 1 |
| Red Phantom Games | — | 1 | — |
| Renegade Software | 1990 | — | 1 |
| Repixel8 | — | 3 | 3 |
| Revolution Software | 1990 | 11 | 3 |
| Ripstone | February 2011 | 2 | 4 |
| Rising Star Games | 2004 | — | 16 |
| Robot House Games | September 24, 2012 | 1 | 1 |
| Robot Teddy | 2019 | 1 | 1 |
| Rockstar Lincoln | 1992 | 2 | — |
| Rockstar London | 2005 | — | — |
| Rocksteady Studios | December 13, 2004 | 6 | — |
| Roll7 | — | 3 | — |
| Rowan Software | 1987 | 1 | — |
| RumbleSushi | 2010 | — | — |
| Runecraft | 1997 | — | 1 |
| Runner Duck | 2017 | 1 | — |
| Sabec Limited | 1993 | 2 | 1 |
| SCE Studio Liverpool | 1984 | 13 | 16 |
| SeaCorpTech | — | 1 | 1 |
| Secret Mode | September 29, 2020 | — | 7 |
| SEGA Europe | 1986 | — | 2 |
| Sega Racing Studio | 2005 | 1 | — |
| Sensible Software | 1986 | 3 | — |
| SFB Games | September 2, 2002 | 3 | 2 |
| Sierra Europe | — | — | 1 |
| Silicon Dreams Studios | March 1994 | 7 | — |
| Silverball Studios | 2002 | 2 | — |
| Size Five Games | 2008 | 1 | 1 |
| Slightly Mad Studios | 2009 | 5 | 1 |
| Slitherine Software UK Limited | 2000 | 9 | 70 |
| Soft Leaf Studios | 2019 | 1 | — |
| Software Creations | 1985 | 10 | — |
| Software Projects | 1983 | 1 | 2 |
| Sokaikan | September 18, 2017 | 1 | — |
| Sold-Out Software | 1997 | 1 | 5 |
| Somethin' Else Sound Directions Ltd. | 1991 | 1 | — |
| Space Lizard Studio | — | 2 | 1 |
| Spiral Circus | October 23, 2018 | 1 | — |
| Spiral House | 1998 | 1 | — |
| Splash Damage | April 30, 2001 | 6 | — |
| Sports Interactive | July 21, 1994 | 33 | — |
| Stainless Games | 1993 | 5 | 3 |
| State of Play | 2008 | 5 | 5 |
| Strategy First | 1988 | 4 | 39 |
| Studio 33 | 1998 | 3 | — |
| Sumo Digital | 2003 | 16 | 1 |
| Sumo Nottingham | 2016 | 1 | — |
| Sunscorched Studios | April 11, 2019 | 2 | 1 |
| Super Rare Games | October 25, 2017 | — | 1 |