State Route 420 (SR 420) is a 4.7-mile-long (7.6 km) east-west state highway in Gibson County, Tennessee, connecting the community of Fruitland with the town of Gibson.

SR 420 begins in Fruitland at an intersection with US 45W/SR 5.

It heads east through farmland and rural areas for several miles before entering Gibson and coming to an end at an intersection with SR 186 just north of downtown.

[1] The entire route of SR 420 is a rural two-lane highway.

[2] The entire route is in Gibson County.