League of Denial is a 2013 book, initially broadcast as a documentary film, about traumatic brain injury in the National Football League (NFL), particularly concussions and chronic traumatic encephalopathy (CTE). The documentary, entitled League of Denial: The NFL's Concussion Crisis, was produced by Frontline and broadcast on PBS. The book was written by ESPN reporters Mark Fainaru-Wada and Steve Fainaru. The book and film devote significant attention to the story of Mike Webster and his football-related brain injuries, and the pathologist who examined Webster's brain, Bennet Omalu. The film also looks closely at the efforts of researchers led by Ann McKee at Boston University's Center for the Study of Traumatic Encephalopathy, where the brains of a number of former NFL athletes have been examined.

Concussions and play-related head blows in American football have been shown to be the cause of chronic traumatic encephalopathy (CTE), which has led to player deaths and other debilitating symptoms after retirement, including memory loss, depression, anxiety, headaches, stress, and sleep disturbances.