At the headwaters of the Nissequogue River it derives its name from the Native American term for "overflowed land. The Hauppauge Industrial Park, located at the edge of the hamlet, is the largest on Long Island, and by some accounts the second largest in the nation. The park has over 1,300 companies, and employs over 55,000 Long Islanders. The companies in the industrial park provide the tax revenue that makes up the bulk of the Hauppauge school district's budget. As a result, school taxes for residents are relatively low, while the budget for schools is actually higher than usual. It is noted for its well funded schools, with multiple internet-accessible computers in every classroom, many after school activities, etc. See Hauppauge Computer Works.
There were 7,006 households out of which 34.2% had children under the age of 18 living with them, 68.6% were married couples living together, 8.4% had a female householder with no husband present, and 20.1% were non-families. 16.4% of all households were made up of individuals and 4.5% had someone living alone who was 65 years of age or older. The average household size was 2.85 and the average family size was 3.21.
In the CDP the population was spread out with 24.0% under the age of 18, 6.2% from 18 to 24, 31.2% from 25 to 44, 27.7% from 45 to 64, and 11.0% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 98.2 males. For every 100 females age 18 and over, there were 95.5 males.
The median income for a household in the CDP was $98,178, and the median income for a family was $94,819. Males had a median income of $58,103 versus $38,750 for females. The per capita income for the CDP was $30,915. About 2.0% of families and 3.1% of the population were below the poverty line, including 2.2% of those under age 18 and 3.2% of those age 65 or over.