Nassau is an unincorporated community in eastern Sussex County,Delaware, United States. It lies just off Delaware Route 1 west of Lewes and northeast of the town of Georgetown, the county seat of Sussex County. Its elevation is 26 feet (8 m). Although it is unincorporated, it has a post office, with the ZIP code of 19969.
Nassau, like much of central Delmarva, is part of the Salisbury, Maryland-Delaware Metropolitan Statistical Area.