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.

The Port Jefferson Branch is a rail line and service owned and operated by the Long Island Rail Road in the U.S. state of New York. The branch splits from the Main Line just east of Hicksville and runs northeast and east to Port Jefferson. Several stations on the Main Line west of Hicksville are served primarily by trains bound to/from the Port Jefferson branch, so LIRR maps and schedules for the public include that part of the Main Line in the "Port Jefferson Branch" service.