Closter (pronounced [ˈkloːsta] or [ˈkloːstə], with a long o) is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 8,373, reflecting a decline of 10 (-0.1%) from the 8,383 counted in the 2000 Census, which had in turn increased by 289 (+3.6%) from the 8,094 counted in the 1990 Census.
Closter, first settled in 1704, was formed by an Act of the New Jersey Legislature on January 1, 1904, from portions of Harrington Township. On March 29, 1904, Harrington Park was created from portions of Closter, Harrington Township and Washington Township. After the turn of the 20th century, Closter changed from being sprawling estates and farms into an upper middle class suburban town.