Long Hill is a census-designated place (CDP) in the town of Groton in New London County, Connecticut, United States.

As of the census[3] of 2000, there were 3,534 people, 1,741 households, and 741 families residing in the CDP.

There were 1,924 housing units at an average density of 1,295.0 per square mile (500.0/km2).

The racial makeup of the CDP was 79.06% White, 6.48% African American, 1.25% Native American, 7.56% Asian, 0.34% Pacific Islander, 1.36% from other races, and 3.96% from two or more races.

48.7% of all households were made up of individuals, and 19.1% had someone living alone who was 65 years of age or older.