Catholic Encyclopedia

The Catholic Encyclopedia: An International Work of Reference on the Constitution, Doctrine, Discipline, and History of the Catholic Church, also referred to as the Old Catholic Encyclopedia and the Original Catholic Encyclopedia, is an English-language encyclopedia published in the United States designed to serve the Catholic Church. The first volume appeared in March 1907 and the last three volumes appeared in 1912, followed by a master index volume in 1914 and later supplementary volumes. It was designed "to give its readers full and authoritative information on the entire cycle of Catholic interests, action and doctrine".

The Catholic Encyclopedia was published by the Robert Appleton Company (RAC), a publishing company incorporated at New York in February 1905 for the express purpose of publishing the encyclopedia. The five members of the encyclopedia's Editorial Board also served as the directors of the company. In 1912, the company's name was changed to The Encyclopedia Press. Publication of the encyclopedia's volumes was the sole business conducted by the company during the project's lifetime.