State Route 15 (SR 15) is a north–south route that transects the U.S. state of Georgia, east of its centerline. Its northern end is at the border of North Carolina, just north of Dilliard; its southern end is at the Florida border, just south of Folkston, where the actual highway continues southwards as Florida SR 15. SR 15 northbound merges into U.S. Route 441 (US 441) in Watkinsville. Then, the two highways run concurrently from there to the border with North Carolina.

Much of SR 15 experiences a relatively low traffic volume, especially in areas south of Athens, but it is still an important corridor for motorists traveling between Athens and coastal areas of Georgia, as it remains the shortest and arguably fastest route between Athens and I-16 east.

SR 15 enters Georgia just south of Folkston as a four-lane highway, along with US 1, US 23, US 301, and SR 4. Just north of Folkston, US 301 branches off to the north while the other four routes plus SR 121, head northwest. After about ten miles, State Routes 15 and 121 also branch off from US 1/US 23/SR 4, as a two-lane highway, crossing US 82/SR 520 (South Georgia Parkway) in Hoboken. The two state routes continue northwest through Blackshear, where they cross US 84. After that, the two state routes continue to stay together, heading north through the community of Bristol. Soon after, SR 121 branches off to the north while SR 15 heads northwest to rejoin US 1 and SR 4 at Baxley. North of Baxley, the three routes continue, remaining a four-lane highway all the way to the Altamaha River. Approximately ten miles past the river crossing, SR 15 branches off to the northwest again, where SR 29 begins and follows SR 15. At Vidalia, State Routes 15 and 29 turn west and follow US 280 for several miles to the community of Higgston. The two routes head north from there through the community of Tarrytown and then on to Soperton. SR 29 heads northwest of Soperton while SR 15, along with SR 78, continues north, intersecting with I-16, and goes to Adrian. The two state routes continue northwest to Wrightsville, where SR 78 departs eastward. SR 15 continues by itself through the adjacent cities of Tennille and Sandersville. Through these cites, most of SR 15 has been widened to four lanes, and it briefly picks up SR 24. North of Sandersville, SR 15 crosses the Fall Line Freeway and then heads north through the community of Warthen and onto Sparta. Through Sparta, SR 15 makes a few turns, briefly picking up SR 16 and SR 22. North of Sparta, it picks up SR 77, and continues north through White Plains and Siloam. At Siloam, SR 77 departs to the north while SR 15 continues northwest to Greensboro, passing beneath I-20, but without direct access. In Greensboro, SR 15 makes two more turns, briefly following US 278 through downtown. SR 15 continues northwest to Watkinsville, after which it joins US 441 and remain together as a mostly four-lane highway throughout the rest of their course in Georgia.

The two routes, along with several others, circle around the east side of Athens along the Athens Perimeter freeway and head north through the town of Nicholson and around the east side of Commerce via a bypass. The highways then interchange with I-85, and head between the towns of Baldwin and Cornelia, where they become a limited access freeway for a short time and rejoin US 23. The three routes remain together and head through the cities of Tallulah Falls, Clayton, and Dillard before crossing into North Carolina.

State Route 15 Alternate (SR 15 ALT) is a series of streets, roads, and highways that form a north–south-oriented route in two counties of the northeastern part of the state of Georgia. This route's southern terminus is in Athens at the intersection of US 441/SR 15 and SR 10 Loop (locally known as "The 10 Loop" or "Loop 10") and Macon Highway. This route eventually becomes Milledge Avenue, and winds by the campus of the University of Georgia. This street features stately homes and mansions, some of which house college fraternities and sororities. As SR 15 ALT leaves Athens, it overlaps US 129, where it is known as Jefferson Road. Upon entering Jefferson, SR 15 ALT splits from US 129 and becomes an independent route. Its northern terminus is north of the city of Commerce at its intersection with US 441 (sometimes referred to as the Commerce Bypass) and SR 59.