The term `` Long Island '' often refers only to the mostly suburban counties of Nassau and Suffolk because Brooklyn and Queens are part of New York City . Stretching northeast into the Atlantic Ocean , Long Island contains four counties , two of which are boroughs ( Queens and Brooklyn ) of New York City , and two of which ( Nassau and Suffolk ) are mainly suburban or rural . In popular usage , the term `` Long Island '' generally refers only to Nassau and Suffolk counties in order to differentiate them from New York City , though all four counties on the island are part of the New York metropolitan area .