Marblehead is an unincorporated community in Adams County, Illinois, USA, just south of Quincy. Illinois State Route 57 is the main auxiliary route through the town and travels north to the business district of Quincy or south to Interstate 72 (near Hannibal, Missouri).
The community is part of the Quincy, IL–MO Micropolitan Statistical Area.
Marblehead is prone to flooding and during the Flood of 2008, the town was flooded with water from the Mississippi River. A temporary "Lake Marblehead" was formed when the flood plain flooded. It was named so as a satire joke.