Simeon Rabban Ata, also Simeon Rabban-ata and sometimes Simeo Rabban Ara, was a high representative of Syriac Christianity in the 13th century. Among other things, he was tasked by the Mongols, such as Khans Ogodei and Guyuk, to handle Christian matters. He was in charge of establishing Christian churches in the Mongol realm, and had contact with some of the Christian envoys and missionaries that passed through the area. He was known to have met with André de Longjumeau and Ascelin in Tabriz in 1245, as they were on their own missions to the Mongols.
He himself visited the Mongol court in 1235-1240, and was an intermediary between Eastern and Western Christianity, corresponding with the Pope, such as when he transmitted a profession of faith by the Jacobite patriarch Ignatius II in 1247, and gave to André de Longjumeau a letter in which the primacy of Rome was being recognized.