State Route 43 (SR 43) is a south to north highway in Tennessee that is 56.79 miles (91.39 km) long.

It goes northeast as a divided four-lane highway, overlain by US 45E, and SR 186 for a short distance, before leaving Three Way and crossing into Gibson County.

They then leave Medina and continue north to enter Milan and have an intersection with SR 187 before becoming an undivided four-lane as it passes through residential areas.

The highway then crosses the South Fork of the Obion River to enter Weakley County.

As a result, a new divided, limited-access four-lane US 45E was constructed around the east side of Martin where more land was available, and the original SR 43 designation was revealed on signposts.

North of Martin, SR 43 rejoins US 45E and continues as an undivided four-lane highway to South Fulton, where it breaks free again as a signed secondary highway and follows the original US 45E Business Route through town to the Kentucky state line while US 45E bypasses to the west.