State Route 13 is a south–north route from the Alabama border at Wayne County, Tennessee to the Kentucky border in Montgomery County.

State Route 13 begins at the Alabama state line and continues north to parallel the Natchez Trace Parkway for a few miles near Collinwood. It intersects US-64 / SR-15 / SR-99 at Waynesboro. A few miles north of Waynesboro near the Perry County line, SR-48 heads northeast to Hohenwald and SR-13 turns west to Flat Woods where it resumes its northward direction and begins to parallel the Buffalo River. SR-13 follows the Buffalo River north, intersecting US-412 / SR-100 / (SR-20 unsigned) at Linden. North of Linden, SR-438 from Centerville crosses the Buffalo River and joins highway 13 at Beardstown for a few miles until SR-438 leaves Route 13 in DePriest Bend heading west to terminate at US-412 / SR-100 / (SR-20 unsigned) on the east bank of the Tennessee River near Perryville. Route 13 passes through Lobelville before its junction with Interstate 40, at Exit 143. It then continues north to its intersection with US-70 / SR-1 at Waverly. From Waverly, State Route 13 continues north to intersect SR-49 in Erin. Route 13 then turns east to Cunningham where it connects with SR-48 and continues north to cross the Cumberland River at Clarksville. In Clarksville, it becomes concurrent to U.S. Route 41A Bypass. After going up the west side of the city, it leaves the bypass and heads east to US-79, which it follows to Kentucky.