BMX, an abbreviation for bicycle motocross, is a cycle sport performed on BMX bikes, either in competitive BMX racing or freestyle BMX, or else in general on- or off-road recreation. BMX began when young cyclists appropriated motocross tracks for fun, racing and stunts, eventually evolving to specialized BMX bikes and competitions.

BMX began in the early 1970s in the United States when children began racing their bicycles on dirt tracks in southern California, inspired by the motocross stars of the time. By the middle of that decade, the sport achieved critical mass, and manufacturers began creating bicycles designed especially for the sport. Nowadays, BMX continues to be a very popular action sport, with millions of active BMX riders around the globe.