Kei car is the smallest category of Japanese, expressway-legal motor vehicles. 'Kei' is diminutive for kei-jidōsha,, "light automobile" or "compact automobile". With restricted dimensions and engine specifications, owners benefit firstly from lower taxes and insurance rates which lead to a lower overall cost of ownership. And in most rural areas, importantly, they were also exempted from the general Japanese shako shōmeisho (車庫証明書) parking-space ownership requirement to legally buy a motor vehicle at all, as street parking is generally restricted in Japan. Japan's carmakers also make microvans and kei trucks within this legal category.

The Honda N-Box is a kei car produced by Honda for the Japanese market. Together with the N-WGN, N-One and N-Van, it is part of the renewed N lineup of kei class city cars from Honda. The use of the letter "N" in the name was previously used for the late 1960s and 1970s N360.