Monongalia County is a county 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. Named Monongalia as it was the land of the Monongahela River, it was home to a few settlers and Native American Tribes of Delaware, Shawnees, and Iroquois.