Castle Hill is a town in Aroostook County, Maine, United States. The population was 425 at the 2010 census.
According to the United States Census Bureau, the town has a total area of 36.15 square miles (93.63 km2), of which, 35.69 square miles (92.44 km2) of it is land and 0.46 square miles (1.19 km2) is water.
As of the census of 2010, there were 425 people, 181 households, and 127 families living in the town. The population density was 11.9 inhabitants per square mile (4.6/km2). There were 211 housing units at an average density of 5.9 per square mile (2.3/km2). The racial makeup of the town was 98.6% White, 0.2% African American, 0.7% Native American, and 0.5% from two or more races. Hispanic or Latino of any race were 0.7% of the population.
There were 181 households, of which 23.2% had children under the age of 18 living with them, 61.9% were married couples living together, 6.1% had a female householder with no husband present, 2.2% had a male householder with no wife present, and 29.8% were non-families. 21.5% of all households were made up of individuals, and 6.1% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.72.