Fountain City is a neighborhood in northern Knoxville, Tennessee, in the southeastern United States. Although not a census-designated place, the populations of the two ZIP codes that serve Fountain City— 37918 and 37912— were 36,815 and 18,695, respectively, as of the 2000 U.S. census. At the time of its annexation by the city of Knoxville in 1962, Fountain City was the largest unincorporated community in the United States.