Dewey Beach is an incorporated coastal town in eastern Sussex County, Delaware, United States. According to the 2010 census, the population of the town is 341, an increase of 13.3% over the previous decade. It is part of the rapidly growing Cape Region and lies within the Salisbury, Maryland-Delaware Metropolitan Statistical Area. In 2011, the NRDC awarded Dewey Beach with a 5-Star rating in water quality. This award was given only to 12 other locations, one being neighboring Rehoboth Beach. Out of the 30 states with coastline, the Delaware Beaches ranked number 1 in water quality in 2011.

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.