The Saints' street gang has become an icon after merging with the Ultor Corporation and turning into a media empire. However, their newfound success attracts unwanted attention from the Syndicate, a powerful international crime organization. When a fellow actor attempts to "research" his role for the Saints movie, they rob a bank and get caught, leading to their leader Gat's release on condition that they give up two thirds of their revenue made in Stilwater.
To take revenge on the Syndicate, the Saints relocate to Steelport, a city suffering from economic failure. The Syndicate has taken control over Steelport through three gangs: The Morningstar, Luchadores, and Deckers. The Saints now need to take control of the city, fighting other gangs and reclaiming their former glory.
Saints Row: The Third is a sandbox game that focuses on third-person action, free-roaming driving, and urban warfare. The protagonist explores the city of Steelport, performs missions, and engages in Activities, Strongholds, and Flashpoints. Completing missions earns money, weapons, cars, and gang reputation. The player can use their reputation as experience points to upgrade weapons and cars. Money is used to customize the appearance, outfits, and headquarters of the gang. The Initiation Station system allows players to upload and download characters online. Additionally, money can be used to buy shops and properties in Steelport, generating a steady income for the gang.
New features include novelty weapons and an improved combat system. Players can call down airstrikes on enemy camps or use remote control electric bugs to control vehicles. Health regenerates faster out of combat, and almost every action can be sped up by holding down a special button.
The game also features co-op mode, where the second player participates in all missions and activities, receiving credit for their completion. Co-op features require a single-use online pass, but there is no competitive multiplayer mode.