Hellgate: London is a computer game developed by Flagship Studios. The design of the game is similar in a number of ways to the Diablo series. This is due to influence of Flagship Studios co-founders including a number of ex-Blizzard North employees, including Diablo series creators Erich Schaefer and former President David Brevik. The other founders are Erich's brother Max Schaefer, former Blizzard North Vice President Bill Roper, and Diablo II producer Kenneth Williams.

Hellgate: London is a role-playing game (RPG) which has some first-person shooter (FPS) elements in a post-apocalyptic setting. Hellgate(HGL) Palladium(PD) and Hellgate(HGL) Powerleveing is the most valuable form of currency in Hellgate: London. Gameplay is based heavily on the character's stats, as per role-playing games. The FPS element of Hellgate: London will be seen in the Hunter faction and will require some skill to use. Soft-aim will be included in the game as a form of aim assistance.

The game, like its spiritual predecessor Diablo, builds heavily upon the core design of Roguelikes. Notably it embraces the game design philosophy of using random generation to allow for a high degree of replayability and countless unique gameplay experiences.