The American Council of Learned Societies, founded in 1919, is a private non-profit federation of sixty-eight scholarly organizations.

ACLS is best known as a funder of humanities research through fellowships and grants awards. ACLS Fellowships are designed to permit scholars holding the Ph.D. or equivalent to devote a full year to research and writing in such fields as Literatures and Languages, History, Anthropology, Political Theory, Philosophy, Classics, Religion, Biblical Studies, Archeology, the History of Art, Linguistics, Musicology.

Among the Council’s publications is the American National Biography, published in early 1999; it consists of a 24-volume collection of approximately 17,500 biographies of significant individuals in American history. An online version was released in 2000. The Dictionary of Scientific Biography has articles on significant scientists from antiquity to modern times. The Dictionary of the Middle Ages, completed in 1989, consists of 13 volumes covering the years 500-1500 and examines the Latin West, Slavic, Byzantium, and Islam.

During the late 1950s, the Council greatly encouraged Hans Wehr in his writing of the first English edition of his Dictionary of Modern Written Arabic (1962).

Since 2002 ACLS has also sponsored online an electronic e-book collection, ACLS Humanities E-Book (HEB) http://www.humanitiesebook.org/. HEB is a collection of 1700 full-text, fully searchable, high-quality books in the humanities available online. These books are recommended and reviewed by scholars for their continuing value to students and scholars. This project was originally funded by the Andrew W. Mellon Foundation http://www.mellon.org/ and is a collaboration of twelve learned societies http://www.humanitiesebook.org/societies.html, over 95 university presses http://www.humanitiesebook.org/publishers.html, and almost 600 subscribing institutions http://www.humanitiesebook.org/subscribinginsts.html.