Hellgate:London is a dark fantasy action game that blends a single player RPG experience with an online multiplayer component. Set in a post-apocalyptic version of London where monsters roam the streets and many buildings are destroyed or otherwise unsafe, Hellgate lets players choose one of six classes, which are divided into three archetypes. The game is notable for its reliance on randomly generated stats, maps, monsters, and loot, intended to make it highly replayable.

Hellgate comes with auto aiming, and different views for each class. Melee fighters must stick to third-person perspective, while ranged fighters can switch between first and third. the single player campaign lasts over 20 hours and upon completion, a player can create an elite character automatically for online play. There are crafting modes, including to save space in one's limited inventory, which can yield rare items. The game also has many story quests in its offline mode.

Flagship Studios released two major content updates for the game in early to mid-2008.

The game's online mode was available in both free to play and subscription editions, with free players limited in character slots, inventory, and activities like access to exclusive PvP zones and the ability to create guilds. Hellgate: London is notable for the offer of "lifetime subscriptions" that went for $200 to a limited number of pre-orders.

Facing a horde of financial problems, Flagship Studios, the makers of Hellgate: London, went under in 2008, and the game's US and European servers were shut down in February 2009, just over a year after release. While the single player offline campaign is still playable, the only online server left is run by HanbitSoft in Korea, which has also taken on development.