Sunless Sea is a survival/exploration role-playing video game with roguelike elements developed by Failbetter Games. The game was released on 6 February 2015 for Windows and OS X following a successful Kickstarter campaign to crowdfund the project. The game takes place in the universe of Failbetter's browser adventure game Fallen London, in which Victorian-era London has been moved beneath the earth's surface to the edge of the Unterzee, a vast underground ocean. On 11 October 2016, the game's first downloadable content Zubmariner was released, which allows players to explore beneath the surface of the "zee". A sequel, Sunless Skies, was announced in September 2016. It surpassed its funding goals on Kickstarter and was released on 31 January 2019.