Motocross is a form of motorcycle racing or all-terrain vehicle racing held on enclosed off-road circuits and is widely considered the world's most popular form of motorcycle racing. Motocross is derived from the French, and was originally called Scrambling when the sport was invented in the UK. The first known race took place at Camberley, Surrey in 1924. The name "motocross" is a contraction derived from the words "Motorcycle" and "Cross Country". Motocross is often abbreviated as MX.

Motocross tracks are often quite large (around 1 to 2 miles) and incorporate natural terrain features with varying amounts of man made jumps and other features. It is not unheard of for a Motocross track to be made up entirely of hills and turns with no jumps at all. In contrast Supercross is an entirley man made track, comprisingly almost exculsivly of a wide array of jumps and typically held in an indoor stadium.

Due to the size of the track, motocross races typically include 40 racers, incontrast to Supercross where its it is only practical to have about 25.

Races vary in lenght of duration, usually measured in time elapsed plus one or two laps. GP or Pro AMA races tend to be long, eg 30 minutes plus 2 laps. At the other end of the spectrum ameuteur races by beginers can be as short as 10 minutes (or shorter). When the designated time duration of the race is complete a finish line flager indicated via a board or flag signals to the racers that there is one or two laps left, and the race is finsihed by a Racing_flags. Contrasting with motocross, in the "off-road" racing events of Enduro, Hare and Hounds, Hare Scrambles, GP racing, etc. (events which are like motocross, but place a greater emphasis upon reading natural terrain and obstacles over a long period of time at much greater speeds than traditional motocross) there are a set amount of laps or long distance loops to complete or just a maximum time limit to compete under on a natural terrain course, e.g., Baja 1000.

Races are ran in sessions called motos. There are two motos in a race and the riders place in those heats are averaged together to get their overall finish.