Greek Orthodox patriarch of Alexandria, Egypt, and theologian whose discussions with European Protestants concluded with his writing an exposition of Eastern Orthodox doctrine in an attempt at Christian unity.

After becoming a monk at Mt. Athos, Greece, Kritopoulos in 1617 was sent on a tour of leading Anglican and Protestant university centres by the patriarch of Constantinople (now Istanbul), Cyril Lucaris, who sought to integrate Orthodox and Calvinist teaching. After study and exchanges with Anglicans at Oxford (1617–23) and with continental reformers in Germany, Switzerland, and Italy until c. 1630, he returned to the East and was made an Egyptian bishop in 1631; by 1636 he had been consecrated patriarch of Alexandria. He subscribed to the decisions of the 1638 Council of Constantinople that condemned Cyril for his Protestant leanings.

While at Helmstedt, Ger. (1624–25), Kritopoulos wrote in Greek “Confession of the Catholic and Apostolic Eastern Church,” a treatise on the traditional Orthodox creed. The confession reverts to the doctrinal expressions of the early Greek Church Fathers as a basis for mutual understanding among the contending Christian communions. Thus, he emphasizes the biblical and devotional simplicity of primitive Christianity, with its emphasis on the divine Trinity and the reconciliation of fallen man with God through a mystical, sacramental relationship to Christ's divinity and sacrifice. Critical of aspects both in Protestant and Roman Catholic teaching, Kritopoulos maintained an ambiguous position in mediating the contrary theologies.