Tenafly () is a borough in Bergen County, New Jersey, United States. As of the 2010 census, the borough's population was 14,488, reflecting an increase of 682 (+4.9%) from the 13,806 counted in the 2000 Census, which had in turn increased by 480 (+3.6%) from the 13,326 counted in the 1990 Census. Tenafly is a suburb of New York City.
The first European settlers in Tenafly were Dutch immigrants, who began to populate the area during the late 17th century. The name "Tenafly" is derived from the early-modern Dutch phrase "Tiene Vly" or "Ten Swamps" which was given by Dutch settlers in 1688. Other derivations cite a Dutch-language connection to its location on a meadow.
The borough has been one of the state's highest-income communities. Based on data from the American Community Survey for 2013–2017, Tenafly residents had a median household income of $153,381, ranked 13th in the state among municipalities with more than 10,000 residents, more than double the statewide median of $76,475.
Tenafly was incorporated as a borough on January 24, 1894, by an act of the New Jersey Legislature from portions of the now-defunct Palisades Township, based on the results of a referendum held the previous day. The borough was the first formed during the "Boroughitis" phenomenon then sweeping through Bergen County, in which 26 boroughs were formed in the county in 1894 alone. Portions of Palisades Township were acquired based on legislation approved on April 8, 1897.
New Jersey Monthly magazine ranked Tenafly as the 7th best place to live in New Jersey in its 2013 rankings of the "Best Places To Live" in New Jersey.
According to the United States Census Bureau, the borough had a total area of 5.16 square miles (13.38 km2), including 4.59 square miles (11.88 km2) of land and 0.58 square miles (1.50 km2) of water (11.20%).
The borough borders the municipalities of Alpine, Bergenfield, Cresskill, Englewood and Englewood Cliffs in Bergen County; The Bronx in New York City and Yonkers in Westchester County, New York, across the Hudson River.
Tenafly's street plan and overall development were largely determined by its hills and valleys. The eastern part of the borough is referred to as the "East Hill" for its higher elevation in relation to the rest of the borough.