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 from the 2010 census count of 1,901, which in turn reflected a decline of 343 from the 2,244 counted in the 2000 census. Avon-by-the-Sea was incorporated as a borough by an act of the New Jersey Legislature on March 23, 1900, from portions of Neptune City.