Arctodus, also known as the Short-Faced Bear, is a genus of extinct bear. One species, the Giant Short-Faced Bear (Arctodus simus) was the biggest bear ever to have lived. Standing 1.5 metres at the shoulder and equipped with powerful jaws this bear would have been an intimidating sight.

Arctodus seems to have been mainly a carnivore and was by far the most powerful land predator during the Ice Age in North America. It may have attacked bison, deer, and horses, but current research suggests it was more of a scavenger. Compared to modern brown bears it had much longer limbs and was generally more slender. It had a very short, broad muzzle which gives rise to its name, and which gave it a very powerful bite. Its long legs enabled Arctodus to range far and wide in search of carrion and its powerful bite enabled it to crack open bones to reach rich marrow.

The largest known skull of Arctodus was found by a Yukon gold miner. Another fossil from southern Saskatchewan indicates that Arctodus lived there more than 70,000 years ago. Arctodus simus, the largest species, ranged the high grasslands of western North America from Alaska to Mexico, while a lighter-built species (Arctodus pristinus) with smaller teeth inhabited the more heavily wooded Atlantic coastal region.

The short-faced bear belongs to a group of bears known as the Tremarctine bears, which are of New World origin. The earliest member of the Tremarctinae is Plionarctos , which lived in Texas during the Pliocene Epoch (about 5-2 million years ago). It is likely that this genus is ancestral to the Spectacled Bear (Tremarctos) and the short-faced bear. Although the early history of Arctodus is poorly known, it evidently became widespread in North America by the Kansan age (about 800,000 years ago).

The short-faced bear became extinct some 12,000 years ago, perhaps partly because some of its large prey died out earlier, and partly because of competition with the smaller, more herbivorous brown bears that entered North America from Eurasia. Since its demise coincides with the arrival of humans in North America, hunting may also have contributed to its extinction.