The AMA Motocross Championship, also known as Lucas Oil Pro Motocross, is a premier motorcycle racing series in the United States. The championship was founded by the American Motorcyclist Association (AMA) in 1972 and is sanctioned by AMA Pro Racing. The series is managed by MX Sports Pro Racing and is considered the most important outdoor motocross series in the country.

The Pro Motocross started in 1972 with two classes featuring motorcycles with 500 cc and 250 cc engine displacement formulas. In 1974, a 125 cc class was added to the series. As motocross technology progressed, the 500 cc two-stroke motocross bikes became too powerful for most riders. Due to a decrease in the number of participants, the AMA decided to discontinue the 500 cc class after the 1993 season.

In 1996, a women's national championship series was introduced to the Pro Motocross Championship. This provided female riders with the opportunity to showcase their skills and compete at a high level in the sport. With this addition, the championship became more diverse and inclusive, catering to both male and female motocross riders. 

In the past, the AMA Supercross Championship held the title of the world championship in the sport. However, with the introduction of the FIM Supercross World Championship, the AMA Supercross Championship lost its world title status. As a result, the MXGP and AMA Supercross Championship came together in 2023 to form the SuperMotocross World Championship. This new championship will represent the highest level of motocross racing in the world, and it will be sanctioned by both the FIM and AMA Pro Motocross Racing.

Motocross racing in the United States began in the 1970s, when promoters like Bill France started holding races in stadiums within cities. Dirt was imported into the stadiums to create tracks similar to natural terrain motocross tracks. In 1972, Mike Goodwin and Terry Tiernan organized a stadium race in the Los Angeles Coliseum, which became known as the SuperBowl of Motocross. This form of racing later evolved into a separate sport and series called Supercross, which runs in addition to the outdoor Pro Motocross championship. Unlike Supercross, Pro Motocross has two 30-minute plus 2 lap races per round, with the rider with the highest combined points total for the two races being declared the winner. The Pro Motocross schedule runs from May to August and includes 12 rounds of intense competition across some of the most challenging and iconic tracks in the United States.