Cosby is an unincorporated community in Cocke County, Tennessee, United States. Although it is not a census-designated place, the ZIP Code Tabulation Area for the ZIP Code (37722) that serves Cosby had a population of 5,201 as of the 2000 U.S. Census. The community has given its name to the northeastern section of the Great Smoky Mountains National Park, which forms its southern boundary.
Cosby Creek, its source on the crest of the Smokies near Cammerer Ridge, is the valley's main watershed. The creek cuts through the valley, running roughly parallel to Tennessee Route 32 before turning east near Allen Grove and emptying into the Pigeon River. Traditionally, Cosby has been divided into three sections, known simply as "Lower Cosby," "Middle Cosby," and "Upper Cosby." Lower Cosby is the northernmost section, roughly consisting of the area between the mouth of Cosby Creek along the Pigeon River and Jones Cove Road. Upper Cosby, most of which is now part of the national park, consists mainly of the area in the vicinity of the Cosby Campground.