Elsmere is a town in New Castle County, Delaware, United States, bordering the city of Wilmington along Wilmington's western border. According to the 2010 Census, the population of the town is 6,131.

New Castle County is the northernmost of the three counties of the U.S. state of Delaware. As of the 2020 census, the population was 570,719, making it the most populous county in Delaware, with nearly 60% of the state's population of 989,948. The county seat is Wilmington, which is also the state's most populous city.