Halo 5: Guardians is a 2015 first-person shooter game developed by 343 Industries and published by Microsoft Studios for the Xbox One. The plot follows two fireteams of human supersoldiers: Blue Team, led by Master Chief, and Fireteam Osiris, led by Spartan Locke. When Blue Team goes AWOL to track down the artificial intelligence construct Cortana, Master Chief's loyalty is called into question and Fireteam Osiris is sent to retrieve him.

343 Industries started to plan Halo 5 shortly after the release of its predecessor, Halo 4. In late 2012, the team set goals for the game, including larger campaign and multiplayer areas. Like Halo 4, it uses motion capture for character animation. It features new abilities and character designs, but does not feature any offline capabilities or local networking. It has a game engine that scales its resolution to maintain a frame rate of 60 frames per second.

Microsoft announced the game at E3 2013. The game sold five million units within three months and is the fifth-best selling game for the Xbox One. Upon release, Halo 5 received positive reviews from critics, with praise directed at its gameplay, visuals, level design and multiplayer modes. However, the game's single-player campaign met divided responses, with criticism directed at its story, writing, and ending. A sequel, Halo Infinite, was released on December 8, 2021.

Halo 5: Guardians is a first-person shooter game. Players assume the role of powerful "Spartan" supersoldiers with a host of abilities, and use on a combination of guns, grenades, and melee attacks in story-based campaign and multiplayer modes. Players can sprint indefinitely, as opposed to the sprint limits in previous games in the series, though their damage-absorbing shield will not recharge in multiplayer; at top speed, the player character can slide across the ground or charge into an enemy. A thruster pack allows for a speed boost or lateral movements, and players can clamber up ledges to reach higher ground. Every weapon can be aimed while zoomed in, similar to iron sights; sustaining fire will knock players out of the zoomed view. By zooming while airborne, players briefly hover; while aloft, players can target the ground for an area-of-effect attack. The game features new weapons, as well as returning ones with tweaked mechanics.

The game's campaign mode casts the player in the roles of two protagonists, the Master Chief and Jameson Locke. Each character is accompanied by a persistent fireteam of non-player character Spartans—Blue Team for Chief, and Fireteam Osiris for Locke—who are present at all times. During cooperative play, other human players assume control of these Spartans, who each have different loadouts and attributes. Players can direct computer-controlled fireteam members via the d-pad to perform actions such as picking up a weapon, getting into a vehicle, or prioritizing a selected enemy. If a Spartan takes too much damage, they enter an incapacitated state, and can be revived by another fireteam member before dying. The game's difficulty scales to compensate for the number of human players.

Xbox Live multiplayer features a variety of competitive and cooperative game modes. Established four-versus-four arena modes like deathmatch or capture the flag return. New to Halo 5 is Warzone, a 24-player game mode that pit two teams against each other. In addition to fighting the enemy team, players can earn points by capturing locations on the map or defeating computer-controlled bosses; the game ends either when one team destroys the other team's home base, or they earn 1000 points. Players earn requisition or "REQ" points over the course of a match, which can be used to summon weapons, vehicles or powerups into the map based on rewards the player has earned from REQ packs. These packs can be earned in-game via a progression system, or else bought with real-world currency. In ranked play, players complete a series of placement matches to obtain one of seven competitive skill rank ratings, which can go up or down based on winning or losing games.

Halo 5 features an editor called Forge, where players can create their own multiplayer maps. The mode has a new control scheme compared to Halo 4, and new capabilities including scripting tools that can be applied to game objects. Unlike previous first-person shooters in the Halo franchise, Halo 5 does not feature any offline multiplayer capabilities, like split-screen cooperative campaign and multiplayer modes, and has no local networking options. The game was supported via the Halo Waypoint website with player statistics tracking and additional features such as Spartan Companies, where players could band together in groups of up to 100 players and work on completing in-game challenges to unlock cosmetic rewards.

Halo 5: Guardians takes place in the year 2558, eight months after the events of Halo 4. The game follows two fireteams of supersoldiers of the United Nations Space Command (UNSC). Blue Team is led by Master Chief Petty Officer John-117 and is composed of his fellow Spartan-II supersoldiers: Linda-058, an elite sniper; Kelly-087, a scout; and Frederic-104, a hand-to-hand combat specialist. The members of Blue Team are among the last Spartan-IIs left alive. Fireteam Osiris is formed from Spartan-IVs, a newer generation of Spartans. Osiris is led by Jameson Locke, a former assassin and tracker of the Office of Naval Intelligence (ONI). The other members of Fireteam Osiris are Holly Tanaka, a combat technician, engineer, and survivor of a Covenant attack on her planet; Olympia Vale, a political liaison and signals intelligence agent who can speak many alien dialects; and Edward Buck, a veteran trooper who was a main character in Halo 3: ODST.