Winterthur (also Winterthrup) is an affluent unincorporated community in northern New Castle County, Delaware, United States. It lies at the intersection of Delaware Routes 92 and 100, north of the city of Wilmington, the county seat of New Castle County. It is primarily a bedroom community. Its elevation is 269 feet (82 m). Although it is unincorporated, it has a post office, with the ZIP code of 19735.
The community takes its name from the Winterthur Museum and Country Estate. This museum is named after the 6th-greatest city in Switzerland, Winterthur.