Monkey bike is the name given to various small, low-powered motorcycles first made popular by Honda in the 1970s. These vehicles are typically 50-90cc, with a single cylinder four-stroke engine, and have a seat height of 24 inches (60 cm) or less. This gives the rider a crouched appearance, making him look like a stylized image of a squatting monkey.

Numerous similar designs predate the Honda model, notably the World War II parachutist motorcycles such as the Welbike, but these were not commonly known by this name until the Honda design made the type of vehicle commonplace.

The "Dax" model is a 2 seat variant.

In Japan, the small size of the vehicle and the availability of tuning parts has led to a sub-culture of "racing" monkey bikes, with large amounts of money being spent for minute horsepower gains.