棕熊（学名：Ursus arctos）是一种极为庞大的熊，古称罴，体重可达130–700公斤（300–1500磅）。其中灰熊、阿拉斯加棕熊和墨西哥棕熊都分布在北美。

棕熊有毛茸茸的毛皮，呈白色、棕色、黑色或杂色；虽然叫棕熊，但是它们的毛色通常偏灰。在棕熊的背部有一块鼓起来的肌肉，当它们挖洞时，那块肌肉便给予棕熊前肢的力量。它们有一双有力的大手，有1.5米长，一掌拍下去足以杀死一头和自身一样大的马鹿。不像有些大型动物，例如狮子或老虎，它们的爪子（指甲）不能伸缩，由于爪子不能伸缩，它们的爪子不是很灵活。尽管它们的爪子不灵活，那巨大的力量还是致命的。头大而圆。

The brown bear (Ursus arctos) is a large bear distributed across much of northern Eurasia and North America and is the largest terrestrial carnivoran. There are several recognized subspecies within the brown bear species.

While the brown bear's range has shrunk and it has faced local extinctions, it remains listed as a least concern species by the IUCN with a total population of approximately 200,000. As of 2012, this and the American black bear are the only bear species not classified as threatened by the IUCN. However, the Californian, North African (Atlas bear), and Mexican subspecies were hunted to extinction in the nineteenth and twentieth centuries, and many of the southern Asian subspecies are highly endangered. The smallest subspecies, the Himalayan brown bear, is critically endangered, occupying only 2% of its former range and threatened by uncontrolled poaching for its parts. The Marsican brown bear in central Italy is believed to have a population of just 30 to 40 bears.