Ronkonkoma is a hamlet and census-designated place mostly in the Town of Islip, with a small eastern portion in the Town of Brookhaven in Suffolk County, New York, United States. The population was 18,955 at the time of the 2020 census. The Ronkonkoma post office has the ZIP Code 11779, and serves parts of several hamlets and CDPs adjacent to Ronkonkoma. The hamlet is also home to Long Island MacArthur Airport, which is owned and operated by the Town of Islip.