The following highways are numbered 721:
Costa Rica National Route 721
United States Florida State Road 721 (former) Georgia State Route 721 (former) Nevada State Route 721 (former) New Jersey: County Route 721 (Camden County, New Jersey) County Route 721 (Cumberland County, New Jersey) County Route 721 (Hudson County, New Jersey) Ohio State Route 721 Puerto Rico Highway 721 Virginia State Route 721 (1930-1933) (former)