Call of Duty: Warzone was a 2020 free-to-play battle royale first-person shooter game developed by Raven Software and Infinity Ward and published by Activision. It was released on March 10, 2020, for PlayStation 4, Windows, and Xbox One as part of Call of Duty: Modern Warfare (2019) and was subsequently connected to Call of Duty: Black Ops Cold War (2020) and Call of Duty: Vanguard (2021), but did not require purchase of any of the aforementioned titles. Warzone allowed online multiplayer combat among 150 players and featured both cross-platform play and cross-platform progression between the three aforementioned titles.

At launch, the game featured two main game modes: Battle Royale and Plunder. Warzone introduced a new in-game currency system that could be used at "Buy Stations" in and around the map. "Loadout Drops" were a key in-game object allowing players to access and switch between their customized classes, which are pre-selected weapon and perk combinations, and were obtainable through purchase with the Cash currency. At launch, Warzone only offered Trios, a squad capacity of three players; Solos, Duos and Quads were added to the game via post-launch updates.

Upon release, Warzone received generally favorable reviews from critics. Warzone was downloaded by six million people within 24 hours of its initial release; by April 2021, the game surpassed 100 million downloads. A successor to Warzone, initially titled Call of Duty: Warzone 2.0 before it was also shortened to Call of Duty: Warzone, was released on November 16, 2022. A mobile version of Warzone, titled Call of Duty: Warzone Mobile, was announced in March 2022, and was released on March 21, 2024. In June 2023, Activision announced that servers for Warzone would be shut down on September 21, 2023 to focus development on Warzone 2.0.

Warzone is the second main battle royale installment in the Call of Duty franchise, following the "Blackout" mode of Call of Duty: Black Ops 4. Warzone differs from Black Ops 4 by reducing reliance on equipable gadgets and instead encouraging the accumulation of a new in-game currency called "Cash". The game supports up to 150 players in a single match, which exceeds the typical "100 players" size that is seen in other battle royale titles.

At launch, Warzone featured two primary game modes: Battle Royale and Plunder. These game modes were initially playable in a squad capacity of three players ("Trios"); post-launch updates made the modes playable in other squad sizes, such as Solos, Duos and Quads. In addition to Battle Royale and Plunder, several new game modes, including various limited-time modes and the "Resurgence" game mode, have been introduced throughout the course of the game's life cycle. Warzone has also been used to reveal upcoming Call of Duty titles through similar limited-time gamemodes.

The Battle Royale mode is similar to other titles in the genre, where players compete in a continuously shrinking map to be the last player remaining. Players parachute onto a large game map with a basic un-customized pistol and two armor plates, where they encounter other players. Players can pick up most components found in a standard loadout (primary and secondary weapons, lethal and tactical equipment, field upgrades, and "killstreaks") as they search the map for items scattered across the ground and from supply boxes found in designated locations. Players can also pick up additional armor plates for increased protection.

After several minutes have passed within the match, "Loadout Drops" will begin to spawn at various points of the map, allowing players to equip custom loadouts; Loadout Drops can also be purchased by players at a "Buy Station" using Cash. As the game progresses and players are eliminated, the playable area shrinks, forcing the remaining players into tighter spaces; the non-playable areas become contaminated with a yellow gas that depletes health and eventually kills the player if they do not return to the safe playable area.

Character death in Battle Royale does not necessarily translate to player defeat like in other titles. Instead, the mode offers a respawn mechanic which players can take advantage of in various ways. Players who are killed are transported to the "Gulag", where they engage in one-on-one combat with another defeated player, with both players being given the same weaponry. Players may only enter the gulag after their first death in a match. The winner of this combat is respawned into the game. Other methods of respawn are available using the in-game currency system.