Remsenburg-Speonk is a census-designated place (CDP) located in the Town of Southampton, Suffolk County, New York, United States. It consists of the hamlets of Remsenburg and Speonk. As of the 2020 census, Remsenburg-Speonk had a population of 3,110. The population of this CDP and surrounding ones increases in the summer due to summer renters who come out for the beaches and scenery.