Ahatallah (1590 – c. 1655) was a Syrian clergyman chiefly known for his trip to India in 1652, on which he claimed to be the designated "Patriarch of the Whole of India and of China". Apparently, he had previously claimed to be the rightful Patriarch of Antioch and to have received his commission from the Pope; though these claims appear to be exaggerated, he was evidently at least a bishop. His mysterious appearance in, and disappearance from, Portuguese India caused a great uproar there, and resulted directly in a revolt by the Saint Thomas Christians against Portuguese rule and the establishment of an independent Malankara Church.
Ahatallah's biography is obscure. Many earlier scholars, including the Lebanese Orientalist Joseph Simon Assemani and Edward René Hambye, believed he was a Jacobite; a member of the Syriac Orthodox Church. However, later research by Joseph Thekedathu, relying on additional documents found in the archives in the Vatican and Goa, has established further details of his life. He was born in Aleppo, Syria, in 1590, and did enter the Syriac Orthodox Church, eventually being consecrated Bishop of Damascus. While bishop he converted to the Catholic Church, and in 1632 he traveled to Rome. He stayed there for over a year, and became fluent in Italian. Eventually he requested to return to Syria, where he vowed he would bring the Syriac Orthodox Patriarch of Antioch, Ignatius Hidayat Allah, into communion with Rome. What happened thereafter is unclear.