Greenlawn is a hamlet (and a census-designated place) in Suffolk County, New York, United States. The population was 13,286 at the 2000 census. Students primarily attend the Harborfields Central School District. The ratio of Male to Female in the town in percents is 47% male to 53% female and the median age is 39.
Originally known as Old Fields, it became known by the name Greenlawn with the coming of the Long Island Railroad in 1870 or 1871. The LIRR chose the name Greenlawn for its station, apparently to project an idyllic rural/suburban image and foster resort travel to the beaches in Centerport. Greenlawn was well known for its pickle production during the 19th century as well as, to a lesser degree, potato and cabbage farms; the principal commodity, pickles, is still celebrated by the annual Pickle Festival, held by the local Greenlawn-Centerport Historical Association at the John Gardiner Farm.
Greenlawn is located at 40°51′28″N 73°21′57″W / 40.85778°N 73.36583°W / 40.85778; -73.36583 (40.857648, -73.365932).