Gallatin County is a county located in the U.S. state of Illinois. According to the 2020 census, it has a population of 4,946, making it the third-least populous county in Illinois. Its county seat is Shawneetown. It is located in the southern portion of Illinois known locally as Little Egypt. Located at the mouth of the Wabash River, Gallatin County, along with neighboring Posey County, Indiana, and Union County, Kentucky form the tri-point of the Illinois-Indiana-Kentucky Tri-State Area.

Shawneetown is a city in Gallatin County, Illinois, United States. The population was 1,054 at the 2020 United States Census. It is the county seat of Gallatin County.