Carlstadt is a borough in Bergen County, New Jersey, United States. As of the United States 2000 Census, the borough population was 5,917.
Carlstadt was originally formed as a village by an Act of the New Jersey Legislature on March 12, 1860, within Lodi Township. It was named after Dr. Carl Klein, the leader of a group of early German settlers. The Borough of Carlstadt was incorporated on June 27, 1894, formally set off from Bergen Township, at the height of the Boroughitis phenomenon then sweeping through Bergen County.