Old Tappan is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 5,750, reflecting an increase of 268 (+4.9%) from the 5,482 counted in the 2000 Census, which had in turn increased by 1,228 (+28.9%) from the 4,254 counted in the 1990 Census.
Old Tappan was incorporated as a borough by an Act of the New Jersey Legislature on October 18, 1894, from portions of Harrington Township, based on the results of a referendum held two days earlier. The borough was formed during the "Boroughitis" phenomenon then sweeping through Bergen County, in which 26 boroughs were formed in the county in 1894 alone. On April 23, 1896, additional territory was annexed from Harrington Township.