The game setting is on or around a giant ring-shaped structure in space. The ring has plants and animals that live on it. It is very old and was made long ago by a civilization called the "Forerunners." In the game, the year is 2552. In the storyline, humans have created faster than light travel, and now live on many planets and moons in and out of the Solar System, both fictional and real. In the year 2525, humans living on a planet around another star met several alien species. They are grouped together and known as the "Covenant". The Covenant declared religious war on the humans.