The 13th Legislative District (LD) of Suffolk County is located in the northern portion of Long Island, New York. It encompasses the Town of Smithtown and a small portion of the Town of Huntington. The district includes Smithtown, Fort Salonga, Kings Park, San Remo, Nissequogue, Head of the Harbor, and St. James, as well as portions of Commack and East Northport. The district is bounded by Route 25 to the south, Larkfield Road to the west, the Long Island Sound to the north, and the Brookhaven Town line to the east.
It consists of 60 election districts with approximately 78,000 constituents.