The Marathon Trilogy is a science fiction series of first-person shooter computer games from Bungie, originally released for the Macintosh. The name Marathon is derived from the fictional giant interstellar colony ship that provides the setting for the first game; the ship is constructed out of what used to be the Martian satellite Deimos. The three games in the series—Marathon (1994), Marathon 2: Durandal (1995), and Marathon Infinity (1996)—are widely regarded as spiritual predecessors of Bungie's Halo trilogy.
The trilogy is set in the same universe as Bungie's Pathways Into Darkness title.
Source: Wikipedia, "Marathon Trilogy," available under the CC-BY-SA License.