Plainview is a hamlet and census-designated place (CDP) located on Long Island in the town of Oyster Bay, Nassau County, New York, USA. The population of the CDP was 26,217. The Plainview post office has the ZIP code 11803.
Plainview and its neighboring hamlet, Old Bethpage, share a school system, library, fire department, and water district. Law enforcement for the communities is provided by the Nassau County Police Department, with the Second Precinct serving areas north of Old Country Road and Eighth Precinct serving areas south of Old Country Road. Plainview is split between the 2nd congressional district of New York and the 3rd congressional district of New York.