U.S. Route 78 (US 78) is a 233.3-mile-long (375.5 km) U.S. Highway in the U.S. state of Georgia. It travels west to east in the north-central part of the state, starting at the Alabama state line, west of Tallapoosa, where the roadway continues concurrent with the unsigned highway Alabama State Route 4. This is also the western terminus of Georgia State Route 8 (SR 8), which is concurrent with US 78 to the east. The highway serves the Atlanta, Athens, and Augusta metropolitan areas on its path from the Alabama state line to the South Carolina state line, at the Savannah River, on the northeastern edge of Augusta, where it continues concurrent with US 1/US 25/US 278/SC 121. This is also the eastern terminus of SR 10. US 78 travels through portions of Haralson, Carroll, Douglas, Cobb, Fulton, DeKalb, Gwinnett, Walton, Oconee, Clarke, Oglethorpe, Wilkes, McDuffie, Columbia, and Richmond counties.

A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers. When two roadways share the same right-of-way, it is sometimes called a common section or commons. Other terminology for a concurrency includes overlap, coincidence, duplex, triplex, multiplex, dual routing or triple routing.