Hauppauge is a hamlet and census-designated place in the towns of Islip and Smithtown in western Suffolk County, New York, on Long Island. Its population in 2022 was estimated at 20,401 by the U.S. Census Bureau. Despite the official seat of Suffolk County being Riverhead, situated further east, many of the county's government offices are located in Hauppa…Hauppauge is a hamlet and census-designated place in the towns of Islip and Smithtown in western Suffolk County, New York, on Long Island. Its population in 2022 was estimated at 20,401 by the U.S. Census Bureau. Despite the official seat of Suffolk County being Riverhead, situated further east, many of the county's government offices are located in Hauppauge.