Collier's Encyclopedia (full title: Collier's Encyclopedia with Bibliography and Index) was a United States-based general encyclopedia. It was published by Crowell, Collier and Macmillan. It said it was "a scholarly, systematic, continuously revised summary of the knowledge that is most significant to mankind". Many people believed it was one of the three major contemporary English-language general encyclopedias, together with Encyclopedia Americana and Encyclopædia Britannica. They three were sometimes collectively called "the ABCs".