Avon-by-the-Sea is a borough in Monmouth County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 1,933, an increase of 32 (+1.7%) from the 2010 census count of 1,901, which in turn reflected a decline of 343 (−15.3%) from the 2,244 counted in the 2000 census.