Mullet Key is a historic island near Crystal River, Florida. It is located 3 miles south of the main mouth of the Crystal River, and was inhabited by Native Americans in pre-Columbian times. The island was occupied from roughly 500 A.D. to 1500 A.D. and was inhabited by the Deptford and Safety Harbor cultures. Oyster shell middens have been found at the site. On July 3, 1986, it was added to the U.S. National Register of Historic Places.