Greenlawn is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States. Located on Long Island in the Town of Huntington, the population was 13,742 at the 2010 census. Students primarily attend the Harborfields Central School District.

Greenlawn is a station on the Port Jefferson Branch of the Long Island Rail Road near the intersection of Boulevard Avenue and Broadway in Greenlawn, New York, a few blocks north of Pulaski Road. It is the first station east of Huntington on the non-electrified section of the branch.