Georgia State Route 121 is a 238-mile long state route between Charlton County and Augusta. It is part of a three-state multistate route beginning in Florida and ending in South Carolina.

SR 121 begins in rural Charlton County at a junction with Florida State Road 121 and is immediately multiplexed with Georgia State Route 23. At this point, it is called the Okefenokee Parkway. Passing through St. George, it multiplexes with U.S. 1, U.S. 23, U.S. 301, SR 4, and SR 15 in Folkston. Shortly afterwards, U.S. 301 and SR 23 split off. Later in Race Point, U.S. 1, U.S. 23, and SR 4 split off. In Hoboken, the road intersects with U.S. 82 and SR 520. In Blackshear, U.S. 84 and SR 38 are intersected with. North of this intersection, SR 15 splits off. The road briefly multiplexes with SR 203 shortly afterwards. In Surrency, the road intersects with U.S. 341 and SR 27. Later, SR 169, and then SR 144 multiplex with the road. This is for only a short time. A short time later, SR 23 and SR 27 multiplex with the road. In Reidsville, the road intersects with U.S. 280 and SR 30. In Cobbtown, SR 57 splits off. Just south of Metter, Interstate 16 junctions with the road. In Metter, SR 23 splits off. North of Metter, U.S. 80 and SR 26 intersect with the road. North of that junction, the road multiplexes with U.S. 25 and SR 67. SR 23 rejoins the road shortly afterward. In Millen, SR 23 and SR 67 split off. The road briefly multiplexes with SR 24 in Waynesboro. In Augusta, SR 121 multiplexed with U.S. 1, U.S. 25, U.S. 78, U.S. 278, and SR 10 is called Gordon Highway and serves as a major road.

Georgia State Route 121 Bypass is a partial ring road around Waynesboro. It is also signed as US 25 Bypass.

The entire route is in Waynesboro, Burke County.