In the near future of our world, an uprising of artificially intelligent robots led the United Nations to form Overwatch, an international task force of the best and brightest "scientists, soldiers, adventurers, and oddities" in order to combat the threat. After the war, Overwatch was dedicated to peacekeeping and scientific progress, and became a symbol of hope around the world. However, many years of controversy and waning influence came to a head when the UN launched an investigation into alleged human rights violations, which was shortly thereafter followed by an explosion that claimed Overwatch HQ and the lives of two of its most prominent members. This led to the disbanding of the organization. Now a number of heroes from a variety of organizations and walks of life have come together to fill the void Overwatch left.

Overwatch is a first-person shooter in which two teams of six players each battle to complete objectives or hinder their opponents from doing such. Playable heroes are divided into four classes based broadly on the role they are meant to play: offense, defense, tank, and support. Each hero has their own unique abilities and gameplay mechanics, and players can switch to a different hero mid-match in order to better aid their team. Objectives are different on each map, and can include overseeing the delivery of a payload object to a specific location, capturing or defending specific areas of the map, or a combination of the two.

At the conclusion of a match, the server selects and replays a number of highlights from specific players, which both teams must then vote on. The player with the most votes is awarded the "Play of the Game" and earns bonus experience points. Experience goes towards levels, which in turn award players with loot crates that contain random cosmetic items for the heroes. Alternatively, in-game currency can be earned to directly buy certain cosmetic items, and real-world currency can be used to buy additional loot crates.