Unreal Tournament is a 1999 first-person shooter game developed by Epic Games and Digital Extremes. The second installment in the Unreal series, it was first published by GT Interactive in 1999 for Windows, and later released on the PlayStation 2 and Dreamcast by Infogrames in 2000 and 2001, respectively. Players compete in a series of matches of various types, with the general aim of out-killing opponents. The PC and Dreamcast versions support multiplayer online or over a local area network. Free expansion packs were released, some of which were bundled with a 2000 re-release: Unreal Tournament: Game of the Year Edition.

Powered by the Unreal Engine, Unreal Tournament received universal acclaim, often being considered one of the greatest video games ever made, with reviewers praising the graphics, level design and gameplay, though the console ports were noted for having limitations. The design of the game shifted the series' focus to competitive multiplayer action with the releases of sequels Unreal Tournament 2003 in 2002, Unreal Tournament 2004 in 2004, and Unreal Tournament 3 in 2007.

In 2014, a pre-alpha version of a new game in the series was released titled simply Unreal Tournament, with the source code being freely available, but in 2017 Epic ceased development on it when the team transitioned over to Fortnite due both to the team becoming more interested in it than Unreal Tournament and it becoming more successful and gaining a much larger player base.

Unreal Tournament is an arena first-person shooter, with head-to-head multiplayer deathmatches being the primary focus of the game. The single-player campaign is a series of arena matches played with bots, where the player competes for the title of Grand Champion. The player moves up the tournament ladder in order to challenge the current champion, Xan Kriegor, a mysterious being with exceptional skill. Also available is a practice mode, in which, as its name implies, the player practices a match. Match settings (such as score and time limits) can be customized. Also available are "mutators", which drastically alter gameplay aspects, such as "InstaGib", which makes players compete with instant-kill Shock Rifles instead of the normal weapons. Weapons include the Enforcer, the Rocket Launcher and the Ripper, which fires ricocheting blades. Each weapon has two firing modes which have different effects: for example, Rippers can also fire non-ricocheting blades that explode on impact. A special weapon is the Redeemer, which fires a miniature nuke and causes a large and powerful explosion.

Items such as body armor (which reduces damage taken), health packs (which heal players) and damage amplifiers are scattered across levels. Levels are set in a variety of environments, including spaceships, outposts and buildings like castles and monasteries. Many contain features such as elevators (lifts) and teleporters and obstacles such as water and lava. The game is backwards compatible with the majority of Unreal multiplayer maps. The PC version includes a level editor in which players can create their own levels, and the PlayStation 2 version supports the use of a USB keyboard and mouse, enabling players to play in a similar manner to the PC version.

For team matches, bots are used to fill the roles of the player's teammates. The player can choose the bots' skill level or have it automatically adjust to the player's performance. Bots can be further customized by changing attributes such as names, appearance and weapon preferences. In team matches, players can give orders to bots on their team. The PC version supports multiplayer mode over the internet or a local area network (the original Unreal was mainly a single-player game).

Four "bonus packs" were released, each adding maps, characters, or features. For example, Bonus Pack 1 adds "relics" as mutators. Relics are special items that grant a significant advantage to their holder. They include (but are not limited to), the Relic of Vengeance, which creates an explosion when its holder dies, the Relic of Regeneration, which regenerates the health of the holder, and the Relic of Redemption, which makes its holder respawn elsewhere with full health and weapons intact when they would normally die. Bonus Pack 4 adds a new version of Xan Kriegor.

During the Human–Skaarj war, the New Earth Government was formed. Mining was the primary method of financing the war, but was unpopular with the working class, who grew weary of the working conditions and the war. The humans were losing the war, and riots broke out. The Terran system was surrounded by Skaarj forces, but a government team destroyed their mothership, and the Skaarj withdrew. Afterward, revolts and violence among the mining colonies were on the increase, and efforts to deal with them were unsuccessful. The government then came up with the idea of giving the violence an outlet instead. "Consensual murder" was legalized in the year 2291, enabling people to fight to the death under organized conditions. The Liandri Mining Corporation worked with the government and organized leagues and public exhibitions. Soon, these matches became more profitable than mining, and Liandri formed a professional league to compete in a "Grand Tournament", the most popular event in the sport. The game takes place in 2341, fifty years after the fights were first legalized.