The North American beaver is one of two extant beaver species, along with the Eurasian beaver (Castor fiber). It is native to North America and has been introduced in South America and Europe. The North American beaver is one of the official national wildlife of Canada symbols and is the official state mammal of Oregon and NY. North American beavers are widespread across the continental USA, Canada, southern Alaska and some parts of northern Mexico.

They have been known to live as long as 19 years in captivity. They continue to grow throughout their lives and may reach 3 to 4 feet (0.9–1.2 m) long, including tail. Although most adult beavers weigh 40 to 70 pounds (17–32 kg), very old, fat beavers can weigh as much as 100 pounds (45 kg).