Nassau is a town in Rensselaer County, New York, United States.

The Henry Tunis Smith Farm was listed on the National Register of Historic Places in 1975.

The southern town line is the border of Columbia County, New York.

As of the census[7] of 2000, there were 4,818 people, 1,851 households, and 1,330 families residing in the town.

21.4% of all households were made up of individuals, and 8.1% had someone living alone who was 65 years of age or older.