Hillside Lake is a hamlet (and census-designated place) in Dutchess County, New York, United States. The population was 1,084 at the 2010 census. It is part of the Poughkeepsie–Newburgh–Middletown, NY Metropolitan Statistical Area as well as the larger New York–Newark–Bridgeport, NY-NJ-CT-PA Combined Statistical Area.
Hillside Lake is located in the Town of East Fishkill, near the eastern town line. The community surrounds a small lake, also called Hillside Lake.