Leonardo is an unincorporated community and census-designated place located on the north shore of Middletown Township, in Monmouth County, New Jersey, United States. The community is situated along the Raritan Bayshore and is part of the Jersey Shore region of the state. As of the 2020 United States census, the CDP's population was 2,549, a decrease of 208 from the 2,757 enumerated at the 2010 census, which in turn had reflected a decline of 66 from the 2,823 counted at the 2000 census.