Petros is an unincorporated community and census-designated place in Morgan County, Tennessee, United States, located on State Route 116. Its population was 459 at the 2020 census. Petros has its own post office, with the ZIP code 37845. Petros is historically a coal mining town and was also the site of the now closed Brushy Mountain State Penitentiary. Some of the town and coal mine scenes for the movie October Sky were filmed there.