Christiansburg is a town in Montgomery County, Virginia, United States.The population was 21,041 at the 2010 census. It is the county seat of Montgomery County. Christiansburg, Blacksburg and the city of Radford are the three principal municipalities of the Blacksburg–Christiansburg Metropolitan Statistical Area, which encompasses those municipalities, all of Montgomery County, and three other counties.

Montgomery County is a county located in the Valley and Ridge area of the U.S. state of Virginia. As population in the area increased, Montgomery County was formed in 1777 from Fincastle County, which in turn had been taken from Botetourt County. As of the 2020 census, the population was 99,721. Its county seat is Christiansburg, and Blacksburg is the largest town. Montgomery County is part of the Blacksburg-Christiansburg metropolitan area. It is dominated economically by the presence of Virginia Tech, Virginia's third largest public university, which is the county's largest employer.