Tennille is a city in Washington County, Georgia, United States. The population was 1,469 in 2020. It is considered a suburb of Sandersvil…Tennille is a city in Washington County, Georgia, United States. The population was 1,469 in 2020. It is considered a suburb of Sandersville. The Georgia General Assembly incorporated Tennille in 1875. The community was named after Francis Tennille, an early settler.