Marion is an unincorporated community and census-designated place in Franklin County, Pennsylvania, United States. As of the 2020 census, the population was 851. It lies along U.S. Route 11, 6 miles south of Chambersburg and 5 miles north of Greencastle. Interstate 81 passes along the eastern edge of the community, with access from Exit 10. I-81 leads northeastward 37 miles to Carlisle and south 17 miles to Hagerstown, Maryland.