Grimsley is an unincorporated community and census-designated place (CDP) in Fentress County, Tennessee, United States.

The settled part is located on high ground in the center of the CDP, with elevations ranging from 1,700 to 1,800 feet (520 to 550 m).

The west side of the CDP drops into the gorge of the East Fork of the Obey River, with a bottom elevation of 800 to 900 feet (240 to 270 m), and the east side follows the valley of the North Prong of Clear Fork, with an elevation of 1,600 feet (490 m).

Tennessee State Route 85 forms the southwestern edge of the CDP, dropping by switchbacks into the gorge of the East Fork of the Obey and leading 33 miles (53 km) to Livingston.

According to the U.S. Census Bureau, the Grimsley CDP has an area of 10.9 square miles (28.2 km2), all of it land.