Mount Union is a borough in Huntingdon County, Pennsylvania, United States, approximately 44 miles (71 km) southeast of Altoona and 12 miles (19 km) southeast of Huntingdon, on the Juniata River. In the vicinity are found bituminous coal, ganister rock, fire clay, and some timber. A major Easter grass factory is located in the northern quadrant of the borough limits; until May 2007, the facility was owned by Bleyer Industries. The population was 2,447 at the 2010 census.

Huntingdon County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 44,092. Its county seat is Huntingdon. The county was created on September 20, 1787, mainly from the northern part of Bedford County, plus an addition of territory on the east from Cumberland County. The county is part of the Southwest Pennsylvania region of the state.