The 2015 AFC Championship Game football tampering scandal, commonly referred to as Deflategate was a National Football League (NFL) controversy involving the allegation that the New England Patriots tampered with footballs used in the American Football Conference (AFC) Championship Game against the Indianapolis Colts on January 18, 2015. The league announced on May 11, 2015, that it would suspend Patriots quarterback Tom Brady for four games of the 2015 regular season for his alleged part in the scandal. After NFL commissioner Roger Goodell upheld the suspension in an internal appeal, the matter was moved to federal court. On September 3, 2015, Judge Richard M. Berman vacated Goodell's four-game suspension of Tom Brady, due to legal deficiencies such as inadequate notice to Brady, denial of the opportunity for Brady to examine a lead investigator, and denial of equal access to investigative files. On April 25, 2016, the 2nd U.S. Circuit Court of Appeals reinstated Brady's four-game suspension for the 2016 regular season. After losing a request for a rehearing, Brady announced on July 15 that he would not appeal further and would accept the suspension.

The official rules of the National Football League require footballs to be inflated to a gauge pressure between 12.5 and 13.5 pounds per square inch (psi) or 86 to 93 kPa, when measured by the referees. The rules do not specify the temperature at which such measurement is to be made. Per the pressure-temperature law, there is a positive correlation between the temperature and pressure of a gas with a fixed volume and mass. Thus, if a football were inflated to the minimum pressure of 12.5 psi at room temperature, the pressure would drop below the minimum as the gases inside cooled to the colder ambient temperature on the playing field. While footballs deflate naturally in colder temperatures, a deliberately under-inflated football may be easier to grip, throw, and catch, or inhibit fumbling, especially in cold rainy conditions.

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