After defeating their rivals in Stilwater, the Saints Row: The Third gang merges with the Ultor Corporation and becomes a media empire. However, when an actor tries to "research" his role for a Saints movie, they rob a bank and get caught by the Syndicate, an international crime organization. The Syndicate bribes the police and releases the Saints' leader, Gat, and Shaundi, who are then taken to Phillipe Loren to negotiate business. When Gat rejects their offer, a gunfight ensues, and he escapes with Shaundi.
The Saints relocate to Steelport, where they must take control of the city from three rival gangs: The Morningstar, Luchadores, and Deckers. To reclaim their former glory, the Saints engage in urban warfare, fighting other gangs and completing missions that advance the game's story and side missions.
Saints Row: The Third is a sandbox shooting and driving series that focuses on third-person action, free-roaming driving, and urban warfare. The protagonist explores Steelport, performs missions, and completes Activities, Strongholds, and Flashpoints to earn money, weapons, cars, and gang reputation.
Completing missions earns the player experience points, which can be used to upgrade weapons and cars with various features. Money can be used to customize the gang's appearance, outfits, and headquarters, as well as buy shops and properties in Steelport. The game also introduces novelty weapons and a co-op mode, where players can participate in all missions and activities together.
Some missions can be approached in different ways, with choices required by the player. A special button allows almost every action to be sped up, such as when stealing cars. However, there are no health recovery items; instead, health regenerates at a faster rate out of combat.
The game features airstrikes and remote control vehicles, adding new gameplay mechanics. The co-op mode requires a single-use online pass, but has different rules for some activities. There is no competitive multiplayer mode in the game.