Marathon is a first-person shooter video game developed and published by Bungie, and released in December 1994 for the Apple Macintosh.

The game takes place several centuries into the future in outer space and sets the player as a security officer attempting to stop an alien invasion aboard a colony ship named the Marathon.

Gameplay takes place in a real-time, 3D-rendered world of ceilings and floors of various heights and widths, all viewed from a first-person perspective.

The player assumes the role of a nameless security officer aboard a large colony ship called the Marathon, constructed from Mars' moon Deimos.

[3] The game interface includes an overhead map, a motion sensor indicating the positions and movements of both enemies and allied characters through red triangles and green squares respectively, and bars displaying the player's current shield and oxygen levels.

Obstacles include dark and narrow passages, ceilings that crush the player, pits of harmful molten material or coolant, locked doors or platforms that must be activated by remote switches, and puzzles that may involve precise timing and speed to complete successfully.

Rather than restoring lost health by picking up power-ups as in many first-person shooters, the player instead replenishes their shields and oxygen through activating recharge stations placed in walls; if either drops below zero, they die.

Unique among first-person shooters of its time, Marathon has a detailed, complex plot that is fundamental to gameplay and player advancement.

Some terminals that do not need to be accessed to complete the game but still may contain additional plot information, such as engineering documents, crew diaries, or conversations between the ship's artificial intelligences.

However, it lacked mirrors, sloped floors and ceilings, destructible environments, and many of the other advanced features offered by the Build engine.

In addition to being inaccessible by single players, these levels also distinguish themselves from the main game environments by their designs, intended to facilitate smooth multiplayer gameplay: smaller overall level sizes, spacious areas, faster doors and platforms, fewer aliens, heavier weaponry, multiple predetermined player spawn points, strategic placement of power-ups, and an absence of pattern buffers and terminals.

[4] Lead designer Jason Jones stated that the development of Marathon was probably delayed by a month due to time spent playing multiplayer deathmatches.

At the start of the game, the player character is aboard a shuttle returning from the colony to Marathon when an alien ship attacks the system.

As the alien ship departs the system, the officer works with Leela to clear the last remaining Pfhor aboard Marathon before assessing the full damage that has been done.

[7] Gaming historians have referred to Marathon as the Macintosh's answer to the PC's Doom, i.e. a first person shooter killer app.

[2] Super Marathon bears the distinction of being the first console game developed by Bungie, predating Oni and Halo: Combat Evolved.

Though initially only M1A1 (a "total conversion" to M2's engine) could be used to play the first Marathon, Aleph One eventually gained native M1 asset support.

An Aleph One-based port of Marathon for Apple's iPhone and iPad was released for free (the in-game purchase feature is only used to donate to the developer) on the iTunes App Store in July 2011.