Chances are you already own a copy of Overwatch. But in case you don't, you're in luck.
Blizzard has announced that in just over a week Overwatch will be free to play across all platforms. The event will run from November 18th to the 21s and there will be no strings attached.
During the event all heroes, maps, and game modes will be available. All progress will be saved until the day that you may decide to purchase a full copy of the game.
Major new content is coming to Overwatch around the same time as this event, which will most notably include a new character. Named Sombra, she's already become a fan favorite on the public test realm.