In Warhammer 40,000: Space Marine, you are Captain Titus, a Space Marine of the Ultramarines chapter and a seasoned veteran of countless battles. A millions-strong Ork horde has invaded an Imperial Forge World, one of the planet-sized factories where the war machines for humanity's never-ending battle for survival are created. Losing this planet is not an option, but a darker and far more evil threat is lurking large in the shadows of this world.
With an Imperial liberation fleet en route, the Ultramarines are sent in to hold key locations until reinforcements arrive. Captain Titus and a squad of Ultramarine veterans use bolter and chainsword to take the fight to the enemies of mankind.