Alien Breed 3D II: The Killing Grounds is a first-person shooter game developed by Team17 for Amiga. Published by Ocean Software in 1996, it is the fifth game in the Alien Breed franchise, a series of science fiction-themed shooters.

A sequel to Alien Breed 3D, the game continues the story of a space marine who, having recently survived an alien invasion on an extraterrestrial base and now been rescued by the crew on board an Earth spaceship, is caught in another such invasion that he is forced again to fight off on his own for his life. The game differs from its predecessor largely in improved graphics, as well as level editors bundled with the game and its more extensive use of models, especially for the weapons, though some enemies continue to be rendered as 2D sprites. It also retains a two-player deathmatch multiplayer mode.

The game's release was widely anticipated by the Amiga press and community as a contender to Doom. Reviewers praised the graphics, sound effects, and atmosphere, but were divided on the enemy artificial intelligence, level design, and hardware requirements, particularly for the version requiring 4 MB of RAM. The editors shipped with copies of the game attracted numerous player complaints for missing files, and Team17 uploaded a patch for the editors containing the missing files. The game's programmer, Andrew Clitheroe, disliked the result of its development, stating he wished he had used the time he spent on the rendering engine for developing the gameplay and levels, and Team17 admitted that The Killing Grounds did not meet the company's Alien Breed series' standards in gameplay. The game was the last in the series until Alien Breed Evolution, released in 2009.

Alien Breed 3D II: The Killing Grounds is a first-person shooter in which the player guides their character—a lone space marine—across 16 levels, surviving an alien onslaught along the way. The player's character can run, jump, and look vertically. The player utilizes an arsenal of up to ten weapons; they begin the game with a double-barrelled shotgun, and the remainder must first be found and picked up, such as a blaster, a plasma cannon, grenade and rocket launchers, a rifle, mines, and a gun that fires lasers that bounce off walls. Robots armed with energy or submachine guns constitute the bulk of the enemies the player fights with those weapons, but they also include red hellish dogs (the only reappearance from Alien Breed 3D), stick figures, and one-eyed floating monsters. Many of the enemies continue to be displayed as bitmaps, but some, such as the giant bee-like creature, are rendered as 3D models. The weapons the player carries are also now shown as 3D objects.

At the start of each level, a screen of text is drawn, informing the player of their character's circumstances. During combat, the player depletes their weapons' ammunition and must replace one for each by finding and picking up refill packs. The player's character may also sustain injuries, and their energy is replenished after picking up a first aid kit. The player can carry more energy and ammunition than the GUI can display. Some doors are locked, and the player must first find the key to open them. The levels of The Killing Grounds are mission-oriented, with the player instructed to complete a set of tasks, such as destroying a structure. The instructions are relayed as text at the bottom of the screen revealing the player character's inner thoughts. In later levels, an anti-gravity device is found and can be used for brief flights, and it is limited to a few seconds of use before it must be recharged at a fuel terminal. The player can toggle the game's automap feature, which can be panned and zoomed in and out and is automatically drawn as the player discovers new areas. Instead of passwords like the previous game, between levels, up to five games can be saved.

The Killing Grounds has a multiplayer mode that requires connecting two Amiga computers through their serial ports. In this mode, two players fight each other in a deathmatch battle with no enemies and all doors open.

After surviving an alien invasion on the Osiris base and destroying it, Captain Reynolds's escape shuttle is rescued by an Earth space cruiser, the Indomitable, which then sets course for Earth. However, a massive alien spaceship, having detected the shuttle's distress signal, enters the Indomitable's area, docks the cruiser, and commences an attack, taking its crew hostage. Reynolds awakes in the Earth ship's medical bay, isolated from the attack, and soon discovers that he is forced to fight for his survival on his own again.

Reynolds descends to the alien craft through a shaft connecting the two ships, attempting to find the missing Indomitable crew. After a series of fights with the aliens, he comes across a teleporter serving as a transporter between the craft and a planet. He also realizes that he had been lured into their trap, like the marines on board the Indomitable, and finds he is left with no choice but to teleport to the planet and press on. While there, he determines he is inside an alien military compound, and discovers a computer terminal, through which he connects his mind to a vast network of alien minds represented as bright threads. He sees that the threads intertwine, but fail to join or exchange thoughts, and that a large mass had suffered damage, explaining his observation of the aliens' disorganisation.