State Route 178 is a highway that runs northwest-to-southeast through portions of Toombs and Tattnall counties in southeastern Georgia. The route runs from its northwestern terminus at US 1/SR 4 in Lyons to its southeastern terminus at SR 121/SR 144/SR 169 west of Glennville.

The route is co-signed with SR 147 as it crosses from Toombs County into Tattnall County on its way to its southeastern terminus.