State Route 3 (SR 3) is a state highway that runs south-to-north through portions of Thomas, Mitchell, Dougherty, Lee, Sumter, Schley, Taylor, Upson, Pike, Spalding, Henry, Clayton, Fulton, Cobb, Bartow, Gordon, Whitfield, and Catoosa counties in western Georgia, bisecting the state and roughly paralleling I-75. The route runs from its southern terminus at US 19, SR 300, and FL 57 at the Florida state line, 12 miles south-southeast of Thomasville, to its northern terminus at US 41, US 76, and SR 8 at Tennessee state line near Chattanooga.

The route starts at the Florida state line in Thomas County, and is co-signed with US 19 and SR 300 from its inception. SR 3 heads slightly northwest and skirts east past Thomasville, before heading through Pelham to Camilla in Mitchell County. SR 3 turns slightly northeast in Camilla and heads through Baconton, Georgia to Albany in Dougherty County, where its concurrence with SR 300 ends, before turning north and heading to Leesburg in Lee County. In Leesburg, the route turns slightly northwest once more, runs through Smithville, and crosses into Sumter County.

Turning north again, SR 3 continues through Americus and crosses into Schley County, curving slightly northwest to Ellaville. Leaving Ellaville in a northerly direction again, SR 3 bisects Schley County and heads into Taylor County and through Butler into Upson County. Just after entering Upson County, the route turns northwest yet again and runs to Thomaston. Turning back to the north, SR 3 enters Pike County, and runs through Zebulon on its way slightly northeast to Griffin in Spalding County. South of Griffin, SR 3 intersects and begins a concurrence with US 41 and SR 7, in addition to its continued concurrence with US 19. SR 3 also features a brief freeway section as it passes through the western portion of Griffin.

Heading north, the route enters the western portion of Henry County, and heads through Hampton, where the Atlanta Motor Speedway has direct access from the highway, which regularly sees massive backups on weekends when NASCAR races take place there. Continuing north into Clayton County, SR 3 heads through Jonesboro, and crosses I-75 in Morrow.

Heading north through Forest Park, the route crosses first into Fulton County, then crosses I-285, and I-75 again, as well as I-85, in quick succession, as it makes its way through the southern Atlanta suburban communities of Hapeville and East Point, forming one side of the perimeter of Hartsfield-Jackson Atlanta International Airport near Hapeville. Turning north, the route parallels the Downtown Connector very closely, crosses I-20 in downtown Atlanta, and continues north, beginning and ending concurrencies with US 19, US 78, and US 278, as well as forming part of the western boundary of the campus of Georgia Tech. SR 3 subsequently crosses I-75 for a third and fourth time just northwest of where I-75 and I-85 split, and crosses I-285 once more in Vinings, just after having entered Cobb County.

Heading northwest through Marietta and Kennesaw, the route leaves the Atlanta area and heads into Bartow County, through Cartersville and Adairsville, and on into Gordon County. SR 3 heads through Calhoun, crosses I-75 for a fifth time just south of Resaca, and continues to head north into Whitfield County. Heading through Dalton, the route crosses I-75 yet again, before heading northwest into Catoosa County, where it crosses I-75 for the seventh and final time, before reaching its northern terminus at the Tennessee state line, south of Chattanooga.

On April 2, 1980, SR 3 was designated as the 'Andersonville Trail' at the concurrence of SR 3 with US 280 in Americus.

On May 4, 1992, SR 3 was designated as the 'Admiral Mack Gaston Parkway' where SR 3 connects SR 52 and SR 71 in Dalton.

State Route 3 Alternate uses an older routing of US 19 for 15.5 miles (24.9 km) between Thomasville and Meigs. Until recently, this was the SR 3 mainline, while SR 300 served as the state route concurrency for US 19.

State Route 3 Bypass is a short western bypass of the town of Leesburg in Lee County, which was completed in 2009.

The portion of Tara Boulevard in Clayton County that is not covered by US 19/US 41 and SR 3 near Interstate 75 is designated as State Route 3 Connector. The route is little more than a high-capacity set of ramps to and from I-75 and is unsigned. Another instance of State Route 3 Connector occurs in Whitfield County south of Dalton; it connects I-75 to US 41/SR 3 and the Dalton Bypass. A newer instance is located in Marietta, on a stretch of Roswell Road that was formerly SR 120 east of U.S. 41/SR 3.