Glen Head is a hamlet and census-designated place located within the Town of Oyster Bay in Nassau County, New York. As of the United States 2010 Census, the population of Glen Head was 4,697.It is essential to note that with the exception of the Incorporated Villages of Old Westbury and Mill Neck; the villages of Brookville, Old Brookville, Upper Brookville, Muttontown and Roslyn Harbor do not have post offices or zip codes of their own. Consequently, areas within these communities are served by the Glen Head post office and thereby use this hamlet merely for mailing addresses, despite the physical address being within the limits of an incorporated village.