Fairmont is a city in Marion County, West Virginia, USA. The population was 19,097 at the 2000 census. It is the county seat of Marion County^GR6. Established in 1820 as Middletown, then in Monongalia County, it was chartered by the Virginia General Assembly in 1843 as Fairmont, a contraction of "Fair Mountain". Fairmont is nicknamed "The Friendly City" and is also touted as "The Home of the Original Pepperoni Roll". Father's day originated in Fairmont as well.

Fairmont is located in the northern region of the state, along West Virginia's I-79 High Tech Corridor, about 18 miles southwest of Morgantown. Fairmont's National White Collar Crime Center provides nationwide support to law enforcement agencies involved in prevention, investigation, and prosecution of economic and high-tech crime. The NASA Independent Verification and Validation Facility, governed by the Goddard Space Flight Center, houses more than 150 full-time employees and more than 20 in-house partners and contractors.

As of June 2006, Fairmont city council is in the process (depending on votes) of consolidating Fairmont with the unincorporated communities of Marion County, to have a City-County government, the first to do so in West Virginia. This would make Fairmont the 3rd larest city in the state, just behind Charleston and Huntington.

Fairmont State University, established in 1865, is located in Fairmont.