State Route 309 (SR 309), also known as Union Grove Road, is a 2.6-mile-long (4.2 km) east–west state highway in McMinn County, Tennessee.

It serves as the primary access road from Interstate 75 (I-75, Exit 56) to the town of Niota.

It heads east past a few roadside businesses before passing through farmland as a two-lane highway.

It then enters Niota and comes to an end at an intersection with U.S. Route 11 (US 11, Willson Street/SR 2) on the north side of town.

[2] The entire route is in McMinn County.