Loudon is a city in and the county seat of Loudon County, Tennessee, United States. Its population was 4,476 at the 2000 census. It is included in the Knoxville, Tennessee Metropolitan Statistical Area. The city is located in East Tennessee, southwest of Knoxville, on the Tennessee River. Fort Loudoun, the colonial era fort for which the city was named, is located several miles to the south in Monroe County.