State Route 172 (SR 172) is a 28.1-mile-long (45.2 km) state highway that runs southwest-to-northeast through portions of Madison, Elbert, and Hart counties in the northeastern part of the U.S. state of Georgia.

It heads northeast to an intersection with SR 98, northwest of Comer.

It continues to the northeast and crosses over the Broad River into Elbert County.

Shortly afterward, SR 172 crosses into Hart County.

It continues to the northeast until it meets its northern terminus, an intersection with US 29/SR 8/SR 77 in Hartwell.