Space Hulk is a board game for two players produced by Games Workshop. It was originally released in 1989. The game is set in the fictional universe of Warhammer 40,000. In the game, a "space hulk" is a mass of ancient, derelict space ships, asteroids, and other assorted space debris. One player takes the role of Space Marine Terminators, superhuman elite soldiers who have been sent to investigate such a space hulk. The second player takes the role of Tyranid Genestealers, the vanguard of an aggressive alien species which have made their home aboard the derelict ship.

In Warhammer 40,000, the term "space hulk" is used to refer to any massive derelict space ship that drifts through the vacuum of the galaxy without apparent direction. Since the hulks often exit and re-enter the Warp seemingly at random, searching or travelling within them is dangerous in the extreme, however the Imperium often takes the risk of exploring these hulks for valuable millennia-old technology and artifacts. Space hulks may house more than just Genestealers; other threats aboard can include human followers of the dark gods of Chaos, nightmarish Warp Daemons, and Orks who use space hulks as their "standard" method of interstellar travel. The only realistic means of stopping such threats to the Imperium is to send boarding parties to clear out these infested hulks, as they are often so huge that they can easily shrug off all but the heaviest naval firepower while having their own atmosphere and gravity.

Genestealers were described in an entry of the "Aliens and monsters" section of the first edition of Warhammer 40,000 (the "WH40K - Rogue Trader" manual). However Genestealers were redesigned for Space Hulk, being influenced by the xenomorphs depicted in the Alien franchise. The expanded and rewritten game lore cast Genestealers as a sub-species and shock troops of the all-consuming Tyranids alien race, and of particular note is that Genestealers infiltrate/infect the local populace of target planets to cause civil unrest in advance of an invasion of their Tyranid Hive Fleet.

Space Marine Terminators are described in game lore as first company veterans in each Space Marine Chapter, having earned the right to don the sacred Terminator Armor, making them more powerful and resilient but slower than regular Marines, so Terminators are normally used in close quarter battle environments. Space Marine Terminators were originally only used in Space Hulk-type scenarios, but rules were added in White Dwarf magazine and subsequent releases of Warhammer 40,000 for the inclusion of Terminators as a small/elite part of a Marine army on the open battlefield.

Besides a space hulk, similar skirmishes between Space Marine Terminators and Genestealers can also be set in other environments.

The game is set on a modular board made up of various board sections which represent corridors and rooms and which can be freely arranged and locked together like a jigsaw puzzle to represent the interior of a space hulk. One player controls the Space Marine Terminators, and the other player controls the Tyranid Genestealers.

It is an asymmetric game in the following respects:

The pieces are moved by the players through a system of "action points", where each piece has a certain number specified for it. A Terminator piece has few action points; a Genestealer piece has many action points.