The Appalachian State Mountaineers are the athletic teams that represent Appalachian State University in Boone, North Carolina, United States. The Mountaineers compete in Division I of the National Collegiate Athletic Association (NCAA) and were a member of the Southern Conference (SoCon) between 1972 and 2014. On July 1, 2014, Appalachian State moved to the Sun Belt Conference. Appalachian State fields varsity teams in 17 sports, 7 for men and 10 for women. The football team competes in the Division I Football Bowl Subdivision (FBS), formerly I-A, as a result of the transition to the Sun Belt. The wrestling team remains in the Southern Conference because the Sun Belt does not sponsor the sport. In field hockey, another sport not sponsored by the Sun Belt, Appalachian State joined the Mid-American Conference for the 2017 season after playing two seasons as an independent following the demise of its former league, the Northern Pacific Field Hockey Conference (NorPac). While rivalries exist with Sun Belt west division schools such as Troy and Louisiana, Appalachian State's main Sun Belt rivals are east division members Coastal Carolina and Georgia Southern, as well as rekindled rivalries from the days in FCS with recent Sun Belt additions Marshall and James Madison. Historically prior to joining the Sun Belt, Western Carolina and Furman were prominent rivalries.

Appalachian State University is a public university in Boone, North Carolina. It was founded as a teachers college in 1899 by brothers B. B. and D. D. Dougherty and the latter's wife, Lillie Shull Dougherty. The university expanded to include other programs in 1967 and joined the University of North Carolina System in 1971.