Pontoon fenders are a type of fender for an automobile. Unfortunately, two entirely different types of fender are defined by this term. The earlier American meaning did not reach all nations. Later, a European use of the term, with cognates in several languages, was accepted by the British. A fender is a portion of an automobile body that frames a wheel well. ...

Some cars designed in the United States in the 1930s had front fenders which encased a wheel and ended in a teardrop's point which was not connected to a running board or the body of the car. Instead, a bit forward of this point, sheet metal narrower front to rear than the fender itself attached it to the body quite a bit lower than the highest point of the fender and well forward of the front door. The Cord 810 and 812 are possibly the most well-known cars of this design. A bit earlier, the same company made the Auburn boat-tail speedster with this feature on both the front and rear wheels. And several French Carrossiers, notably Figoni et Falaschi made several extraordinary cars with this feature as well.

In Germany during the Second World War, however, additional armor for the treads of tanks was devised. These long boxes were attached to tanks primarily on the top edge, and resembled pontoons to the soldiers. Hence cars which had the front fenders not just melt into the front door but extend back to the rear fenders were called by them, in translation, pontoons. Hence one model of Mercedes-Benz car is called the "Ponton" type. The British took this as the definition, and so use it in such works as the Beaulieu Encyclopedia of the Automobile. The American term for this type of fender might either be "meltaway" or "full fadeaway".