Hauppauge ( /hɔːpɒɡ/) is a hamlet and CDP in the Town of Islip and the Town of Smithtown in Suffolk County, New York, United States. The population of the CDP was 20,100 at the time of the 2000 census.
Its name derives from the Native American Algonquian term for "overflowed land."
Hauppauge is located at 40°49′6″N 73°12′25″W / 40.81833°N 73.20694°W / 40.81833; -73.20694 (40.818205, -73.206878). According to the United States Census Bureau, the Census-Designated Place (CDP) has a total area of 11.0 square miles (28.4 km²), of which 10.8 square miles (28.0 km²) is land and 0.2 square miles (0.4 km²) (1.37%) is water.