This critical edition of Liber IV of the Reuelaciones of Saint Birgitta of Sweden, like its predecessors in this series, bases its text upon the readings of selected, medieval manuscripts. The text of the Editio princeps (impr. B. Ghotan, Lübeck 1491) has been superseded, particularly in those ten Revelations of Liber IV that were also incorporated by Alfonso of Jaen into Liber VIII (Liber celestis Imperatoris ad reges); in this case, the present edition presents a text that has as yet been inaccessible to non-specialist scholars. This edition also contains an Apparatus critic us, an Apparatus f ontium, a Bibliography, an Introduction on the history of the manuscripts and the text, a Glossary, and Indices of grammar, literary sources, names and places. Keywords: St. Birgitta, St. Bridget, Revelation, Vadstena, Spirituality.