Monmouth Beach is a borough in Monmouth County, in the U.S. state of New Jersey, situated on the Jersey Shore in Central Jersey. As of the 2020 United States census, the borough's population was 3,174, a decrease of 105 from the 2010 census count of 3,279, which in turn had reflected a decline of 316 from the 3,595 counted at the 2000 census. The area was first settled in 1668 and grew into a community with the arrival of the Long Branch and Sea Shore Railroad.