Syosset is a hamlet (and a census-designated place) in Nassau County, New York, within the Town of Oyster Bay. It is a designated hamlet located on the North Shore of Long Island. The population was 18,544 at the 2000 census.

Syosset is located at 40°48′46″N, 73°30′3″W (40.812743, -73.500949)US Gazetteer files: 2000 and 1990. United States Census Bureau (2005-05-03). Retrieved on 2008-01-31..

According to the United States Census Bureau, the CDP has a total area of 5.0 square miles (12.9 km²), all land.