Nassau is an unincorporated community in eastern Sussex County, Delaware, United States. It lies just off Delaware Route 1 northeast of the town of Georgetown, the county seat of Sussex County. Its elevation is 26 feet (8 m), and it is located at 38°45′7″N 75°11′16″W﻿ / ﻿38.75194°N 75.18778°W﻿ / 38.75194; -75.18778 (38.7520565, -75.1876854). Although it is unincorporated, it has a post office, with the ZIP code of 19969. Nassau is part of the Seaford, Delaware Micropolitan Statistical Area.