Waldwick () is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 9,625, reflecting an increase of 3 (+0.0%) from the 9,622 counted in the 2000 Census, which had in turn declined by 135 (-1.4%) from the 9,757 counted in the 1990 Census.
Inhabited during the pre-Columbian era by the Lenape Native American tribe, the region surrounding Waldwick was first explored by Europeans when a Dutch trading expedition landed near there in 1610. With the creation of the Nieuw Amsterdam colony in 1624, the present site of the borough became a Dutch possession along with the rest of northeastern New Jersey. During the period from 1624 to 1664 it was sparsely developed by Dutch settlers, mainly for agricultural purposes. With the annexation of Nieuw Amsterdam by the English in 1664 came a nearly instant increase in immigration to the region and the development of several settlements in and around the present borders of the borough.
In the mid-19th century, Waldwick and the surrounding area constituted a small settlement within Franklin Township, an area that encompassed much of northwestern Bergen County. The area's population grew significantly after the Erie Railroad established a train station. On January 1, 1886, Orvil Township was formed from portions of Hohokus Township and Washington Township. The "Boroughitis" phenomenon that swept through Bergen County, in which 26 boroughs were formed in the county in 1894 alone, hit Orvil Township particularly hard, resulting in the formation of five new boroughs created from the nascent township, including Montvale and Woodcliff (now Woodcliff Lake) on August 31, 1894, Allendale on November 10, 1894, Saddle River on November 20, 1894, and Upper Saddle River formed on November 22, 1894. On April 7, 1919, a council of citizens voted to incorporate as the borough of "Waldwick", from the remaining portions of Orvil Township.