Middlesex County is a county located in the U.S. state of New Jersey. As of the United States 2000 Census, the population was 750,162. It is part of the New York Metropolitan Area and its county seat is New Brunswick6. The center of population for New Jersey is located in Middlesex County, in the town of Milltown, just east of the New Jersey Turnpike (see map of location).

There were 265,815 households out of which 34.20% had children under the age of 18 living with them, 57.00% were married couples living together, 10.80% had a female householder with no husband present, and 28.20% were non-families. 22.40% of all households were made up of individuals and 8.70% had someone living alone who was 65 years of age or older. The average household size was 2.74 and the average family size was 3.23.