Mar Gewargis III served as the 121st Catholicos-Patriarch of the Assyrian Church of the East. On 18 September 2015, the Holy Synod of the Assyrian Church of the East elected Mar Gewargis Sliwa to succeed the late Mar Dinkha IV as the head of the Church. On 27 September 2015, he was formally consecrated and enthroned as Catholicos-Patriarch.

Mar Dinkha IV, born Dinkha Khanania was an Eastern Christian prelate who served as the 120th Catholicos-Patriarch of the Assyrian Church of the East. He was born in the village of Darbandokeh (Derbendoki), Iraq and led the Church in exile in Chicago for most of his life.