The Mongols Motorcycle Club, also known as the Mongol Brotherhood or Mongol Nation, is an international outlaw motorcycle club. Originally formed in Montebello, California, in 1969, the club is headquartered in Southern California. Although the Mongols' main presence lies in California, they also have chapters nationwide in 14 states and internationally in 11 countries. Law enforcement officials estimate approximately 2,000 "full-patched" members are in the club. The Mongols are the fifth-largest outlaw biker club in the world, after the Hells Angels, the Bandidos, the Outlaws and the Pagans.

An outlaw motorcycle club, known colloquially as a bikie gang, biker gang or motorcycle gang, is a motorcycle subculture generally centered on the use of cruiser motorcycles, particularly Harley-Davidsons and choppers, and a set of ideals that purport to celebrate freedom, nonconformity to mainstream culture, and loyalty to the biker group.