Crittenden County is a county in the U.S. state of Kentucky. At the 2020 census, the population was 8,990. Its county seat and only municipality is Marion. The county was formed in 1842 and named for John J. Crittenden, senator and future Governor of Kentucky.

Marion is a home rule-class city in Crittenden County, Kentucky, in the United States. It is the seat of its county. As of the 2010 census, the city population was 3,039.