Giants: Citizen Kabuto is a third-person shooter video game with real-time strategy elements. It was the first project for Planet Moon Studios, which consisted of former Shiny Entertainment employees who had worked on the game MDK in 1997. Giants went through four years of development before Interplay Entertainment published it on December 7, 2000, for Microsoft Windows; a Mac OS X port was published by MacPlay in 2001, and the game was also ported to the PlayStation 2 later that year.

In the game, players take control of a single character from one of three humanoid races to either complete the story in single-player mode or to challenge other players in online multiplayer matches. They can select heavily armed Meccaryns equipped with jet packs, or amphibious spell-casting Sea Reapers; the game's subtitle, "Citizen Kabuto", refers to the last selectable race, a thundering behemoth who can execute earthshaking wrestling attacks to pulverize its enemies. The single-player mode is framed as a sequential story, putting the player through a series of missions, several of which test the player's reflexes in action game-like puzzles.

Game critics praised Giants for its state-of-the-art graphics on Windows computers, a humorous story, and successfully blending different genres. Criticisms focused on crippling software bugs and the lack of an in-game save feature. The console version rectified some of the flaws found in the PC versions, at the cost of removing several features. The game initially sold poorly for Windows and PlayStation 2, but it sold well afterwards, and gained a cult following.

In Giants: Citizen Kabuto, players take on the roles of three humanoid races: gun-toting Meccaryns, magic-wielding Sea Reapers, and the gigantic Kabuto. Each player is assigned direct control of a single character. The game's developers, Planet Moon Studios, created this design to encourage players to focus on the action and not to be burdened with micromanagement. Players can customize the controls, which are largely the same for each race, with slight differences for abilities.

The single-player mode consists of a sequence of missions set as an overarching story. Each mission requires the completion of certain objectives to progress to the next mission. The objectives are usually the elimination of enemies or a certain structure, but several of them test the player's eye–hand coordination or require the player to rescue and protect certain units. Players control their characters from a default third person perspective; a first person view is optional. Each race has its own offensive style, and a special mode of fast movement. Killing a creature releases a power-up, which heals or awards weapons to its collector.

The real-time strategy elements of Giants consist of base building and resource gathering, wherein the resources are small humanoids called Smarties. There are a limited number of Smarties in a mission, and players must rush to gather them, or kidnap them from each other to gain an advantage. Players also gather sustenance for the Smarties to make them work; Meccaryn and Reaper players hunt the cattle-like Vimps for meat and souls respectively. The options in building a base are limited; players can neither choose the locations for the structures nor manage their workforce in detail. Players in control of Kabuto need not build a base; instead, the character gains strength and produces subordinate characters by hunting for food. Kabuto consumes Smarties to increase his size and power; at maximum size, he can produce smaller Tyrannosaurus-like units as subordinates. To restore his health, Kabuto eats Vimps and other units (player- and computer-controlled).

Multiplayer mode allows a maximum of five Meccaryn, three Sea Reaper, and one Kabuto player(s) to play in each session. Due to the lack of a game server browser, players connect through online services MPlayer or GameSpy Arcade for the Windows version, and GameRanger for the Mac OS X version. Besides the standard "destroy all enemy bases and units" missions, the multiplayer mode includes deathmatches and "Capture the Smartie (flag)"-type games. Players are permitted either to start with a full base or to build one from foundations.

The game world of Giants is set on a fictional "Island" traveling through space. Its surface comprises grasslands, deserts, and forests, surrounded by azure seas. Players have an unobstructed view of the game world to its horizon, whereas distant objects are slightly blurred to convey a sense of distance. Missions for Meccaryns provide cover to hide behind, large spaces of water for Reapers, and creatures for Kabuto to eat.