Guntersville is a city and the county seat of Marshall County, Alabama, United States. At the 2020 census, the population of the city was 8,5…Guntersville is a city and the county seat of Marshall County, Alabama, United States. At the 2020 census, the population of the city was 8,553. Guntersville is located in a HUBZone as identified by the U.S. Small Business Administration.