Castle Hayne is a census-designated place (CDP) in New Hanover County, North Carolina, United States. The population was 1,202 at the 2010 census, up from 1,116 in 2000. It is part of the Wilmington Metropolitan Statistical Area.

New Hanover County is a county located in the U.S. state of North Carolina. As of the 2020 census, the population was 225,702. Though the second-smallest county in North Carolina by land area, it is one of the most populous, as its county seat, Wilmington, is one of the state's largest communities. The county was created in 1729 as New Hanover Precinct and gained county status in 1739. New Hanover County is included in the Wilmington, NC Metropolitan Statistical Area, which also includes neighboring Pender and Brunswick counties.