Greenlawn is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States.

[2] Students primarily attend the Harborfields Central School District.

Originally known as Old Fields, it became known by the name Greenlawn with the coming of the Long Island Rail Road 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.

[5] According to the United States Census Bureau, the census-designated place (CDP) has a total area of 3.7 square miles (9.6 km2), all land.