State Route 400 (SR 400) is a controlled access state highway in the northern part of the U.S. state of Georgia. It is concurrent with U.S. Route 19 (US 19) from exit 4 (Interstate 285) until its terminus south-southeast of Dahlonega, linking the city of Atlanta to its northern suburbs. SR 400 travels from the Buckhead neighborhood of Atlanta, at Interstate 85 (I-85), to south-southeast of Dahlonega.