The Japanese macaque ( /məˈkɑːk/;Macaca fuscata), historically known as saru ("monkey"), but now known as Nihonzaru (Nihon "Japan" + saru) to distinguish it from other primates, is a terrestrial Old World monkey species native to Japan. It is also sometimes known as the snow monkey from the fact that it lives in areas where snow covers the ground for months each year — no primate, with the exception of humans, is more northern-living, nor lives in a colder climate. Individuals have brown-grey fur, a red face, and a short tail. There are two subspecies.

The Japanese macaque is sexually dimorphic. Males weigh on average 11.3 kg (25 lb) while females average 8.4 kg (19 lb). Macaques from colder areas tend to weigh more than ones from warmer areas. Male average height is 570.1 mm (22.44 in) and female average height is 522.8 mm (20.58 in). Japanese macaques have short stumps for tails that average 92.51 mm (3.642 in) in males and 79.08 mm (3.113 in) in females. The macaque has a pinkish face and posterior. The rest of its body is covered in hair that can be brown, greyish, or yellowish. The coat of the macaque is well adapted to the cold and its thickness increases as temperature decreases. The macaque can cope with temperatures as low as −20 °C (−4 °F).