Karlamagnús saga : A Modern Composition ? Unger’s Karlamagnússaga is still used as a standard edition of the whole « cycle of Charlemagne » in Old Norse. In this book, the saga is divided in ten « branches/ þættir ». We consider this Karlamagnússaga as an existing medieval text, from the beginning to the end. This medieval text, however, does not exist. In order to complete his edition, Unger had to make editorial choices, retain informations and discard others (from small titles to long passages), give a real existence to branches (like the tenth branch) which do not exist in this form in any existing version, put the branches in a specific order, and edit together texts which do not correspond to the same period of redaction, and were probably never meant to be read together. In its final state, Unger’s edition is therefore more a virtual « Vie poétique de Charlemagne », to phrase it in Gaston Paris’s vocabulary, than a faithful rendering of the Old Norse texts related to Charlemagne. As a virtual composition, this « saga of Charlemagne » is nevertheless an interesting witness of the editorial methods used at the time. Through a comparison with all the existing stages of the « cycle », from the oldest medieval versions to the last modern paper copies (like the copy kept at the Bibliothèque Nationale or the Icelandic copies kept at the National Library), and comparisons with other forms of the « Charlemagne cycle », I shall try to investigate the evolutive process of this cyclic composition.