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.

The Illinois Salines, also known as the Saline Springs or Great Salt Springs, is a salt spring site located along the Saline River in Gallatin County, Illinois. The site was a source of salt for Illinois' prehistoric settlers and is now an archaeological site with a large quantity of organic remains. After European settlement of Illinois, the salt springs became part of Illinois' first major industry and were one of the only places in Illinois where slavery was legal after 1818.