L?????tude de l???iconoclasme byzantin, cette crise th??ologique ayant pour cause l???essor du culte associ?? aux images religieuses, a ??t?? un exercice ardu pour les historiens. En effet, les maigres sources disponibles pour cette p??riode sont toutes favorables au culte des images. Bien qu?????crite par un iconodoule convaincu et hostile aux empereurs iconoclastes, la Chronographie de Th??ophane le Confesseur ne m??rite pourtant pas ses ??tiquettes contemporaines de pro-iconophile et d???anti-iconoclaste. Le pr??sent m??moire propose donc de revoir et de nuancer les ??crits de Th??ophane en ce qui a trait au pouvoir imp??rial. Il s???agira de d??montrer que la place des empereurs sur l?????chiquier th??ologique n???a aucune influence sur la repr??sentation du pouvoir, voire et de ceux qui l???exercent, dans la Chronographie. En effet, une analyse rigoureuse des empereurs de la p??riode iconoclaste (717-780) et de la p??riode iconodoule (780-815) prouvera que pour Th??ophane, rien n???est absolu : les iconoclastes ne sont pas d??pourvus de vertu et les iconodoules peuvent agir de fa??on tyrannique. La Chronographie propose ainsi une image complexe du pouvoir imp??rial, qui oblige ?? reconsid??rer les fronti??res entre l??gitimit?? imp??riale et tyrannie. -- The study of Byzantine iconoclasm, a theological crisis caused by the emergence of religious practices centered on divine images, has proven to be a difficult endeavor for historians. Indeed, the few available sources which discuss this period are clearly favorable to this cult of images. Despite having been written by a convinced iconodule who was also hostile to iconoclastic emperors, the Chronicle by Theophanes the Confessor should not be labelled as purely pro-iconophile and anti-iconoclastic. As such, the present thesis will seek to review and relativize the writings of Theophanes with regards to imperial power. This will attempt to demonstrate that in the Chronicle, the place of emperors on the theological playing field has no impact on the representations of power or those who exert it. In fact, a rigorous analysis of emperors from the iconoclastic period (717-780) as well as the iconodule period (780-815) will show that inTheophanes??? mind nothing is absolute: iconoclasts are not devoid of virtue and iconodules can be tyrannical. Hence, the Chronicle presents a complex image of imperial power, one which demands a reconsideration of the boundaries between imperial legitimacy and tyranny.