Georgia State Route 21

State Route 21 (SR 21) is an 84.4-mile-long (135.8 km) state highway that travels southeast-to-northwest through portions of Chatham, Effingham, Screven, and Jenkins counties in the eastern part of the U.S. state of Georgia. The highway connects the Savannah and Millen areas, via Garden City, Port Wentworth, Rincon, Springfield, and Sylvania.

SR 21 formerly had its northern terminus at the South Carolina state line in Augusta. It traveled on the current path of US 25/SR 121 from Millen to Augusta. In the city, it used the path of SR 28 (Broad Street) and the Georgia segment of US 25 Bus.

The highway is part of the Savannah River Parkway which is being considered for inclusion into Interstate 3 (I-3), a future Interstate Highway proposed to connect the Savannah and Knoxville, Tennessee areas.

SR 21 begins at an intersection with the eastern terminus of SR 204 (Abercorn Street) in Savannah. The highway travels to the west-northwest, becoming a freeway, and gains the designation of Interstate 516 (I-516) and the unsigned SR 421. The highways travel concurrently to the west-northwest, then curve to the north-northeast at the interchange with Veterans Parkway. At exit 3, US 17/SR 25 join the freeway from the southwest, and US 80/SR 26 join the freeway from the northeast. Continuing to the north-northeast, the highways have an interchange with I-16, at which point, US 17 departs to the east-southeast, concurrent with I-16. At exit 7, US 80/SR 26 depart to the west-northwest, and the highways turn to the west-northwest. After SR 25 departs, I-516/SR 421 ends, and SR 21 continues its northwestward route. In Port Wentworth, SR 30 joins the highway; north of their interchange with I-95, SR 30 departs to the west-southwest.

SR 21 continues north, leaving Chatham County and entering Effingham County. The highway travels through Rincon and Springfield, then continues northwest, through rural parts of the county, and continues into Screven County. After a brief concurrency with US 301/SR 73 Loop around the western side of Sylvania, SR 21 continues west into Jenkins County. East of Millen, SR 21 turns to the northwest at its intersection with SR 67, then arcs to the northeast of Millen to meet its northern terminus at US 25/SR 121.

The Tom Triplett Parkway is a section of SR 21 located in Port Wentworth on the west side of the Savannah metropolitan area.

It stretches from the Chatham–Effingham county line (roughly the Lake Cherie Road intersection) to the Garden City–Port Wentworth city line (roughly the SR 307 intersection).

In 2000, the Georgia General Assembly passed a resolution to designate this portion of SR 21 in honor of Tom Triplett, a Democrat who served as Mayor of Port Wentworth and as a State Representative for 18 years. Tom Triplett died in 2006, at 71 years of age.