Avalon is a borough in Cape May County, in the U.S. state of New Jersey. It is located on Seven Mile Island. As of the 2020 United States census, the borough's population was 1,243, a decrease of 91 from the 2010 census count of 1,334, which in turn declined by 809 from the 2,143 counted in the 2000 census. The borough's population swells to as many as 45,000 during the summer.