Monongalia County, known locally as Mon County, is located in the U.S. state of West Virginia. As of the 2020 census, the population was 105,822, making it West Virginia's third-most populous county. Its county seat is Morgantown. The county was founded in 1776. Monongalia County is included in the Morgantown, WV Metropolitan Statistical Area, and is the largest county in North-Central West Virginia. It is part of the Pittsburgh media market.

Morgantown is a city in and the county seat of Monongalia County, West Virginia, United States, situated along the Monongahela River. The most populous city in North Central West Virginia and the third-most populous city in the state, Morgantown is best known as the home of West Virginia University. The population was 30,347 at the 2020 census. The city serves as the anchor of the Morgantown metropolitan area, which had a population of 138,176 in 2020.