North Castle is a town in Westchester County, New York, United States. The population was 11,841 at the 2010 census. It has three hamlets: Armonk, Banksville, and North White Plains.
According to the United States Census Bureau, the town has a total area of 26.5 square miles (69 km2), of which 24.1 square miles (62 km2) is land and 2.4 square miles (6.2 km2), or 9.06%, is water.
As of the census of 2000, there were 10,849 people, 3,583 households, and 3,002 families residing in the town. The population density was 450.4 people per square mile (173.9/km2). There were 3,706 housing units at an average density of 153.9 per square mile (59.4/km2). The racial makeup of the town was 92.38% White, 1.76% African American, 0.03% Native American, 3.96% Asian, 0.05% Pacific Islander, 0.63% from other races, and 1.20% from two or more races. Hispanic or Latino of any race were 4.14% of the population.
There were 3,583 households, out of which 44.2% had children under the age of 18 living with them, 74.6% were married couples living together, 6.9% had a female householder with no husband present, and 16.2% were non-families.