State Route 138 is a highway in the U.S. state of Georgia. The highway is a west-to-east route that begins at the junction of SR 92 just north of Fairburn and ends at US 78/SR 10 near Monroe.

The state route travels through the cities of Union City, Riverdale, Jonesboro, Stockbridge, Conyers, Walnut Grove and Monroe.

The route is briefly co-signed with US 23 and SR 42 through Stockbridge, shortly after crossing I-75 and I-675.

State Route 138 Spur is a very short route, about one-half mile in length, in Jonesboro that connects S.R. 138 with U.S. 19, U.S. 41, S.R. 3, and S.R. 54 (Tara Boulevard). Until the early 1990s, it was part of S.R. 138 proper, which ran through downtown Jonesboro at the time. Around that time, a new bypass was built around the north side of the city. It initially received the designation 138 Spur; however, once the bypass was completed, the 138 and 138 Spur designations were swapped and the new 138 Spur truncated to Tara Boulevard on the west side of Jonesboro. Some street signs on the northern bypass, now the S.R. 138 mainline, still anachronistically refer to the road as "Spur 138".