Cerulean is a census-designated place and unincorporated community in Trigg County, Kentucky, United States. At one time, it was a city, incorporated as Cerulean Springs. It lies along Kentucky Routes 124 and 126 northeast of the city of Cadiz, the county seat of Trigg County. Its elevation is 512 feet, and it is located at 36°57′34″N 87°42′36″W / 36.95944°N 87.71000°W / 36.95944; -87.71000. Although it is unincorporated, it has a post office, with the ZIP code of 42215.The community is part of the Clarksville, TN–KY Metropolitan Statistical Area.