Manasquan is a borough in southern Monmouth County, in the U.S. state of New Jersey, on the Jersey Shore. As of the 2020 United States census, the borough's population was 5,938, an increase of 41 (+0.7%) from the 2010 census count of 5,897, which in turn reflected a decline of 413 (−6.5%) from the 6,310 counted in the 2000 census.