Delmar is a town in Sussex County, Delaware, United States, on the Maryland border along the Transpeninsular Line. Its motto is "The Little Town Too Big for One State." The population was 1,597 at the 2010 census, an increase of 13.5% over the previous decade. It is part of the Salisbury, Maryland-Delaware Metropolitan Statistical Area and a suburb of Salisbury, MD. When added with Delmar, Maryland, the total population of the town was 4,600 at the 2010 Census.

Sussex County is located in the southern part of the U.S. state of Delaware, on the Delmarva Peninsula. As of the 2020 census, the population was 237,378, making it the state's second most populated county only behind New Castle and ahead of Kent. The county seat is Georgetown.