The Subaru Rex , also known as Ace, Viki, Sherpa, 500/600/700, Mini Jumbo, Mini Subaru or M60/M70/M80 in various export markets, is a kei class automobile produced from 1972 to 1992 mainly for sale in Japan by Subaru, although it was also sold in Europe, South America, Australia and the Caribbean. The Rex superseded the R-2 as Subaru's kei car, and has been available in commercial use versions as well as in a passenger car version. It underwent major changes in 1976, in fall 1981, and again in late 1986. The second generation Rex (1981–1986) also formed the basis for the larger Subaru Justy.

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.