Merrick is a hamlet and census-designated place (CDP) in the Town of Hempstead in Nassau County, New York, United States. As of the 2010 census, the CDP population was 22,097. The name Merrick is taken from the word Meroke (oyster bed), the name of the ancestral homeland of the Algonquian tribe formerly indigenous to the area. It is served by the Merrick station on the Long Island Rail Road on the Babylon line.
According to the United States Census Bureau, the CDP has a total area of 5.2 square miles (13 km2), of which 4.2 square miles (11 km2) is land and 1.0 square mile (2.6 km2), or 19.27%, is water.
Merrick has a climate that is bordering upon hot-summer humid continental (Dfa) and humid subtropical (Cfa.) The Cfa zone is found along Merrick's coast. The average monthly temperatures in the town centre range from 31.7 °F in January and 74.8 °F in July.  The local hardiness zone is 7b.
As of the census of 2000, there were 22,764 people, 7,524 households, and 6,478 families residing in the CDP. The population density was 5,423.3 per square mile (2,092.7/km2). There were 7,602 housing units at an average density of 1,811.1/sq mi (698.8/km2).