Lyndhurst is a township in Bergen County, New Jersey, United States. As of the 2010 United States Census, the township's population was 20,554, reflecting an increase of 1,171 (+6.0%) from the 19,383 counted in the 2000 Census, which had in turn increased by 1,121 (+6.1%) from the 18,262 counted in the 1990 Census.
Lyndhurst was originally formed as Union Township on February 19, 1852, from portions of Harrison Township. While it was still Union Township, portions of territory were taken to form Rutherford (as of September 21, 1881), Boiling Springs (April 17, 1889; now known as East Rutherford) and North Arlington (March 11, 1896). On May 15, 1917, the area was reincorporated by an Act of the New Jersey Legislature as the Township of Lyndhurst, based on the results of a referendum held one week earlier. The township is named for Lord Lyndhurst.