Hamilton County is a county located in the U.S. state of Tennessee. It is located in the southern part of East Tennessee on the border with Georgia. As of the 2020 census, the population was 366,207, making it the fourth-most populous county in Tennessee. Its county seat is Chattanooga, located along the Tennessee River. The county was named for Alexander Hamilton, the first secretary of the treasury. Hamilton County is one of 95 counties within Tennessee.