Ashoroa (named after its type locality Ashoro, Hokkaido) is an extinct genus of desmostylian, aquatic, herbivorous mammal. Fossils of Ashoroa have been found on Hokkaido, Japan (43°18′N 143°48′E / 43.3°N 143.8°E, paleocoordinates 44°36′N 141°24′E / 44.6°N 141.4°E) and were dated to the late Oligocene. Ashoroa is the smallest and one of the oldest desmostylians with an estimated body length of 168 cm (66 in). It is known from a rib, a humerus, a femur, and three vretebrae of the single species and holotype, Ashoroa laticosta.