Southern Avenue is one of three boundary streets between Washington, D.C., and the state of Maryland.

Following a southwest-to-northeast line, Southern Avenue begins at the intersection of South Capitol Street in Southeast, Washington, D.C., and Indian Head Highway on the Maryland side.

It runs for approximately 7 miles (11 km) to its other end at Eastern Avenue in Northeast, Washington, D.C., with an uncompleted gap between Naylor Road SE and Branch Avenue SE.

[1] One of the first residential developments on Southern Avenue was Fairfield, a cluster of luxury homes at the intersection of Highview Terrace SE and 34th Street SE in the Summit Park neighborhood.

[2] The Southern Avenue bridge over Suitland Parkway was the first orthotropic deck girder bridge built in Washington, D.C.[3]