Shimun X (Syriac: ܫܡܥܘܢ / Shemʿon, died c. 1638) was Patriarch of the Shemʿon line of primates of the Church of the East, from c. 1600 to c. 1638. He is claimed both by the Chaldean Catholic Church and the Assyrian Church of the East. Upon accession to the patriarchal throne, he moved his seat from Urmia to Salmas, and also resided in Khananis near Qodshanis. He succeeded Patriarch Shimun IX Dinkha who was in full communion with the Catholic Church. Unlike his predecessor, who was officially recognized by Rome as the Patriarch of the Chaldeans, Shimun X was not formally recognized by the Catholic Church because his election was based on hereditary principle, reintroduced after the death of his predecessor. Hereditary succession was considered an unacceptable practice by the Rome. In 1616, contacts between patriarch Shimun X and the Catholic Church were initiated, upon arrival of Catholic missionaries to the region. Patriarch composed a profession of faith, that was sent to Rome for assessment. Upon examination, Shimun′s profession was found inadequate, and he was not received into communion with the Catholic Church. Similar attempt was made in 1619, but wit no final conclusion. Because of such complex situation, his legacy was viewed differently along denominational lines, and claimed by both sides. He is considered as pro-Catholic by the Chaldean Catholic Church, and also as non-Catholic by the Assyrian Church of the East.^[1][2][3]

• Patriarch of the Church of the East
• List of patriarchs of the Church of the East
• List of Chaldean Catholic patriarchs of Babylon