Galactic Civilizations I: Ultimate Edition is a turn-based strategy game developed by Stardock Entertainment. The game takes place in a future where the Terran Alliance has developed the Hyperdrive technology and shared it with four other races. The player's objective is to colonize and populate the systems with class 15 or better types of planets.

Players will select a political party at the beginning of the game that will provide hints and choose the intelligence of rival races. The player will command humanity on its way to the stars and achieve victory through one of four ways: Political, Technological, Cultural, and Conquest, which can be reached by controlling resources and how they are used. The game offers various editors that allow players to create custom maps, game environments, and entire campaigns. The Ultimate Edition includes the Altarian Prophecy expansion.