Avon-by-the-Sea (often called simply Avon) is a borough in Monmouth County, New Jersey, United States, As of the 2010 United States Census, the borough's population was 1,901, reflecting a decline of 343 (-15.3%) from the 2,244 counted in the 2000 Census, which had in turn increased by 79 (+3.6%) from the 2,165 counted in the 1990 Census.