Unam Sanctam Catholicam is a website dedicated to educating people about Catholic heritage through the study of Catholic history. Our site features a host of historical essays on a rich variety of subjects of interest to readers interested in Catholic history.

This site was founded in 2012 by Phillip Campbell, as an extension of a blog of the same name founded in 2003. Most essays on this site were written by Phillip Campbell, although others have contributed as well. Full citations can be found at the bottom of each essay.

Our goal is to become the biggest repository of scholarly historical essays of Catholic interest on the internet. To help us in this goal, please consider making a donation. Please note, Unam Sanctam Catholicam is owned by the publishing company Cruachan Hill Press; your card statement may show a donation to Cruachan Hill Press.

If you are an author who would like to contribute essays to this site, please visit the contact page and send us a message.