The brown bear is an organism.
The brown bear ( Ursus arctos ) is a large bear with the widest distribution of any living ursid . It is one of the two largest terrestrial carnivorans alive today , rivaled in body size only by its close cousin , the polar bear ( Ursus maritimus ) , which is much less variable in size and averages larger due to this . Ursus is a genus in the family Ursidae ( bears ) that includes the widely distributed brown bears , the polar bear , and black bears .