In the 13th century Persia, dominated by the Mongols, a Byzantine princess, Maria Paleologina, stood out greatly in the court of Abaqa Khan, her husband. The Il-Khanate of Persia was then an empire precariously balanced between Islam, dominant in its territories and Christianity that was prevailing in its court and in the diplomatic relations. The role of Maria, a fervent Christian, was decisive in her husband’s policy and in that of any of his successors. Her figure deserves a detailed study and that is what we propose in this paper.