Eta Sigma Phi is the national honorary collegiate society for students of Latin and/or Greek. Members are elected by local chapters which have been chartered by the society. The purposes of the Society, in the words of the Constitution, are "to develop and promote interest in classical study among the students of colleges and universities; to promote closer fraternal relationship among students who are interested in classical study, including inter-campus relationship; to engage generally in an effort to stimulate interest in classical study, and in the history, art, and literature of ancient Greece and Rome."

The Archives of Eta Sigma Phi, the National Classics Honorary Society, were established at the Hewes Library of Monmouth College in Monmouth, Illinois, by vote of the Eta Sigma Phi Board of Trustees in 2004. The purpose of these archives is to serve as a permanent repository for back issues of the Nuntius (the newsletter of Eta Sigma Phi) and other records of the national society. Members are encouraged to donate memorabilia to the collection, which is open to scholars and to the general public by appointment. Copies of documents can be obtained by mail for a modest fee. The archives are maintained by the staff of the Monmouth College Archives with the assistance of Dr. Thomas J. Sienkewicz, Minnie Billings Capron Professor of Classics at Monmouth College and the former Executive Secretary of Eta Sigma Phi.