Zareh I. (Simon Payaslian, Armenian Զարեհ Ա Փայասլեան, born February 14, 1915 in Marash, † February 18, 1963 in Antelias ) was from 1956 to 1963 " Catholicos of the Great House of Cilicia " of the Armenian Apostolic Church.
When forced exodus of Armenians from Cilicia of the seven year-old Simon fled with his parents to Aleppo, where he attended school. After a year of studies at the Jesuit School of Aleppo in 1930, he joined the newly founded seminary of Catholicosate of Cilicia in Antelias a. In 1935, he received as a celibate ordained a priest and studied from 1936 in Brussels Oriental and Byzantine Studies. After a brief teaching career at the Seminary of Antelias he became vicar and prelate of the Archdiocese of Aleppo. In 1947, he received episcopal consecration.
After a long Sedisvakanz he was elected under difficult circumstances on 20 February 1956, a large majority on the Armenian Catholicos of Cilicia. Catholicos Vazken I of Etchmiadzin had left the meeting before election under protest. Zareh was consecrated I of (only ) two Armenian and Syrian Orthodox bishop.
Zareh I. extended the jurisdiction area of the Catholicosate of Cilicia from Greece to Iran and to the United States and thus exacerbated the contradictions to the Catholicos of Echmiadzin. Under him the Cilician Catholicos joined the World Council of Churches, and sent observers to the second Vatican Council of the Roman Catholic Church. From the intra-church dispute sad and drawn, succumbed Zareh I. only 48 years old of a heart attack.