Mar Shimun may refer to any of the following Patriarchs of the Church of the East:
Shemon Bar Sabbae, (c. 329–c. 341), Church of the East Shimun II (1365–1392), Church of the East Shimun III (1403–1407), Church of the East Shimun IV (1437–1497), Church of the East Shimun V (1497–1501), Church of the East Shimun VI (1503–1538), Church of the East Shemon VII Ishoyahb (1538–1551), Church of the East Shimun VIII Yohannan Sulaqa (1553–1555), first Patriarch of the Chaldean Catholic Church Shimun IX Dinkha (1580–1600), Patriarch of the Chaldean Catholic Church Shimun X Eliyah (1600–1638) Shimun XI Eshuyow (1638–1656) Shimun XII Yoalaha (1656–1662) Shimun XIII Dinkha (1662) 1681–1700, Patriarch who broke the Communion with Rome. Successors became leaders of the Assyrian Church of the East Shimun XIV Shlemon (1700–1740), Assyrian Church of the East Shimun XV Maqdassi Mikhail (1740–1780), Assyrian Church of the East Shimun XVI Yohannan (1780–1820), Assyrian Church of the East Shimun XVII Abraham (1820–1860), Assyrian Church of the East Shimun XVIII Rubil (1860–1903), Assyrian Church of the East Shimun XIX Benyamin (1903–1918), Assyrian Church of the East (assassinated) Shimun XX Paulos (1918–1920), Assyrian Church of the East Shimun XXI Eshai (1920–1975) (assassinated), Assyrian Church of the East
See also List of patriarchs of the Church of the East List of Chaldean Catholic Patriarchs of Babylon