Old Bethpage is a hamlet and census-designated place (CDP) located on Long Island in the Town of Oyster Bay, Nassau County, New York, United States. The population of the CDP was 5,523 at the 2010 census. It is served by the Old Bethpage Post Office, ZIP code 11804.
Old Bethpage and its neighboring hamlet, Plainview, share a school system, library, fire department and water district. Law enforcement for the community is provided by the Nassau County Police Department's Eighth Precinct.
In 1695, Thomas Powell bought about 10,000 acres (40 km2) from local Indian tribes, including the Marsapeque, Matinecoc, and Sacatogue, for 140 English pounds. This land, which includes present day Bethpage, East Farmingdale, Farmingdale, Old Bethpage, Plainedge, Plainview, South Farmingdale, and part of Melville, is known as the Bethpage Purchase and is approximately 3.5 miles (5.6 km) east to west and 5 miles (8.0 km) north to south.
Powell called his land Bethphage, because it was situated between two other places on Long Island, Jericho and Jerusalem, just as the biblical town of Bethphage (meaning "house of figs") was situated between Jericho and Jerusalem. Today, the Long Island place formerly called Jerusalem is known as Wantagh and Island Trees, while the placename Jericho is unaltered. Over time, Bethpage was spelled without the second "H".