Bruin is a word for the brown bear (Ursos arctos), or for any bear, usually poetically or archaically.

The word entered the English language via William Caxton's 1485 translation of a Flemish version of the legend of Reynard the Fox. Bruin is the bear, named for his color; the Middle Dutch word for brown is bruun.

It is a popular nickname and mascot in sports. Some teams using this name include

Professional sports

• Boston Bruins, National Hockey League
• Providence Bruins, American Hockey League

Collegiate sports

• University of California, Los Angeles (UCLA)

• Albion College
• Belmont University
• Bellevue University
• Bethany College (California)
• Brown University
• George Fox University

Bruin, Pennsylvania is a borough of Butler County, Pennsylvania in the United States.

BRUIN is an acronym for BRown University INteractive Language , a programming language developed at Brown University for the IBM System/360.

BRUIN was also the name of the British Army's tactical communications system deployed in northwestern Europe from the 1960s to 1985.