The Catholic Encyclopedia, also referred to as the Old Catholic Encyclopedia and the Original Catholic Encyclopedia, is an English-language encyclopedia published in the United States. 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 Robert Appleton Company, 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.