Call of Duty: Vanguard is a 2021 first-person shooter game developed by Sledgehammer Games and published by Activision. It was released on November 5 for PlayStation 4, PlayStation 5, Windows, Xbox One, and Xbox Series X/S. It serves as the 18th installment in the overall Call of Duty series. Vanguard establishes a storyline featuring the birth of the special forces to face an emerging threat at the end of the war during various theatres of World War II.

The game received mixed reviews from critics, with praise towards the entertainment value of the campaign and multiplayer, and the graphics, but criticism for its writing, Zombies mode, and lack of innovation. It failed to meet the sales expectations of Activision.

Vanguard's campaign features similar gameplay mechanics previously introduced in Modern Warfare, such as the player being able to mount wielded weapons to flat surfaces, interact with doors and execute takedowns. New gameplay features allow the player the ability to use a more advanced tactical approach in combat such as blind firing from behind cover, breaking through destructible environmental elements or creating new paths to complete objectives by climbing walls.

Vanguard's multiplayer mode introduces a new game mode to the series, titled "Champion Hill", a successor to the mode "Gunfight", a 2v2 arena mode previously featured in Call of Duty: Modern Warfare and Call of Duty: Black Ops Cold War. Champion Hill tasks players with surviving as long as possible in a squad-based deathmatch, round-robin tournament. Season 2 of Vanguard introduces "Arms Race", a large-scale game mode where two teams of 12 players attempt to capture five bases, or destroy them; players can also earn cash from kills and complete objectives to buy custom loadouts and killstreaks. A new feature introduced to the Call of Duty series through Vanguard's multiplayer is "Combat Pacing". This allows the player to have more control over the selection of multiplayer game modes through three pre-defined pacing filters favoring different playstyles. As an addition to the returning Gunsmith system, Vanguard's multiplayer features a "Caliber system", which brings greater destructibility and reactive environments to maps through different ammunition types.

As with Cold War, Vanguard is integrated with Warzone, allowing players to progress and use weapons, operators and other cosmetics items across both titles, in addition to the existing Modern Warfare and Cold War items in Warzone. Like prior Call of Duty installments since 2019, Vanguard's multiplayer is also fully cross-platform play compatible, with support for cross-generation gaming regarding eighth and ninth generation home video game consoles.

The cooperative Zombies mode returns in Vanguard, developed by Treyarch in collaboration with Sledgehammer Games. The mode is considered an expansion of the Dark Aether story, and acts as a prologue to Black Ops Cold War's story. At launch, the game features a new map titled "Der Anfang", which combines aspects of round-based survival gameplay with the objective-based gameplay of Outbreak and Onslaught, both new gamemodes introduced in Cold War. Gameplay elements from Cold War return in Vanguard, such as Essence and Salvage currencies, and Dark Aether-powered field upgrades, in addition to classic Zombies gameplay items like perks and the Pack-a-Punch machine. A new gameplay feature, the Altar of Covenants, allows players to purchase randomized buffs every round, allowing a variety in combat builds. Post-launch updates for Zombies feature additional objectives for Der Anfang, including a main quest for story progression, as well as new Covenants and field upgrades. An additional map, "Terra Maledicta", was also added to the game in February 2022 as part of the Season 2 content update. Classic round-based maps were announced for Vanguard in April 2022, with the first map, a remake of the Call of Duty: World at War map "Shi no Numa", released in Season 4. The second round-based map, "The Archon", was released in Season 5, which was also the final map released for the mode.

The campaign story of Vanguard is told throughout various points in time in a non-chronological order.

In August 1941, Australian Army demolitionist Private Lucas Riggs (Martin Copping) is stationed at Tobruk as part of the Rats of Tobruk garrison. After a failed ambush attempt against an Afrika Korps convoy, the Rats are assigned to recover supplies for the British Army. They manage to find intelligence relating to General Erwin Rommel, and destroy an enemy depot in the process, but are detained by British Major Henry Hamms (James Frain) for insubordination. In October 1942, during the Second Battle of El Alamein, the Rats are ordered by Hamms to form a defensive line, but Riggs disobeys the command and tries to retake a hill and call in bomber support with fellow Rat Private Desmond "Des" Wilmont (Nikolai Nikolaeff) supporting him. The two of them succeed, though Des is killed in action. Angered by the disregard for the Rats' contribution to the fight, Riggs punches Hamms out of frustration, resulting in him facing prison time.