Map - Suffolk County, New York (Suffolk County)

Suffolk County is the easternmost county in the U.S. state of New York. It is mainly located on the eastern end of Long Island, but also includes several smaller islands. According to the 2020 United States census, the county's population was 1,525,920 making it the fourth-most populous county in the State of New York, and the most populous excluding the five counties of New York City. Its county seat is Riverhead, though most county offices are in Hauppauge. The county was named after the county of Suffolk in England, from where its earliest European settlers came.

Suffolk County incorporates the easternmost extreme of the New York City metropolitan area. The geographically largest of Long Island's four counties and the second-largest of the 62 counties in the State of New York, Suffolk measures 86 mi in length and 26 mi in width at its widest (including water). Most of the island is near sea level, with over 1,000 miles of coastline.

Like other parts of Long Island, the high population density and relative closeness to New York City means that the economy has a mix of industry and science satellite to the city alongside more rural activities like agriculture, a fishery and tourism. Major scientific research facilities in Suffolk County include Brookhaven National Laboratory in Upton, Cold Spring Harbor Laboratory in Huntington, and Plum Island Animal Disease Center on Plum Island. The county is also home to several major universities, including Stony Brook University and Farmingdale State College.

Suffolk County was part of the Connecticut Colony before becoming an original county of the Province of New York, one of twelve created in 1683. From 1664 until 1683 it had been the East Riding of Yorkshire. Its boundaries were essentially the same as at present, with only minor changes in the boundary with its western neighbor, which was originally Queens County but has been Nassau County since the separation of Nassau from Queens in 1899.

According to the Suffolk County website, the county is the leading agricultural county in the state of New York, saying that: "The weather is temperate, clean water is abundant, and the soil is so good that Suffolk is the leading agricultural county in New York State. That Suffolk is still number one in farming, even with the development that has taken place, is a tribute to thoughtful planning, along with the excellent soil, favorable weather conditions, and the work of the dedicated farmers in this region."