Patriarch of Moscow in the context of Epanokalimavkion

The 2018 Moscow–Constantinople schism is an ongoing schism between the Russian Orthodox Church (ROC, also known as the Moscow Patriarchate) and the Ecumenical Patriarchate of Constantinople, which began on 15 October 2018 when the former unilaterally severed full communion with the latter.

The resolution was taken in response to a decision of the Holy Synod of the Ecumenical Patriarchate of Constantinople of 11 October 2018, confirming its intentions to grant autocephaly to the Orthodox Church of Ukraine in the future. The decision also stated that the Holy Synod would immediately: reestablish a stauropegion in Kyiv, i.e. a church body subordinated directly to the ecumenical patriarch; revoke the "Letter of issue" (permission) of 1686 that had given permission to the patriarch of Moscow to ordain the metropolitan of Kiev and lift the excommunications which affected the clergy and faithfuls of two unrecognized Ukrainian Eastern Orthodox churches. Those two unrecognized churches, the Ukrainian Autocephalous Orthodox Church (UAOC) and the Ukrainian Orthodox Church – Kyiv Patriarchate (UOC-KP), were competing with the Ukrainian Orthodox Church (Moscow Patriarchate) (UOC-MP) and were considered "schismatics" (illegally segregated groups) by the Patriarchate of Moscow, as well as by the other Eastern Orthodox churches.

Patriarch Filaret (secular name Mykhailo Antonovych Denysenko Михайло Антонович Денисенко, born 23 January 1929) is a Ukrainian religious leader, currently serving as the primate and Patriarch of the Ukrainian Orthodox Church – Kyiv Patriarchate. The Orthodox Church of Ukraine, that he left in 2019, views him as the Honorary Patriarch emeritus, while the Ecumenical Patriarchate of Constantinople recognises him as former Metropolitan of Kyiv.

He was formerly the Metropolitan of Kiev and the Exarch of Ukraine in the Patriarchate of Moscow (1966–1992). After joining the Kyiv Patriarchate, he was defrocked and in 1997 excommunicated by the ROC. On 11 October 2018, the Patriarchate of Constantinople reinstated him in church communion. However, while restored to the episcopate, the Ecumenical Patriarchate never recognised him as Patriarch and views him as the former Metropolitan of Kyiv. On 15 December 2018, the Ukrainian Orthodox Church of the Kyiv Patriarchate united with the Ukrainian Autocephalous Orthodox Church and some members of the Ukrainian Orthodox Church (MP) into the Orthodox Church of Ukraine; the Ukrainian Orthodox Church of the Kyiv Patriarchate thus ceased to exist.

The Cathedral of Vasily the Blessed (Russian: Собор Василия Блаженного, romanized: Sobor Vasiliya Blazhennogo), known in English as Saint Basil's Cathedral, is an Orthodox church in Red Square of Moscow, and is one of the most popular cultural symbols of Russia. The building, now a museum, is officially known as the Cathedral of the Intercession of the Most Holy Theotokos on the Moat, or Pokrovsky Cathedral. It was built from 1555 to 1561 on orders from Ivan the Terrible and commemorates the capture of Kazan and Astrakhan. It was completed, with its colours, in 1683.

The original building, known as Trinity Church and later Trinity Cathedral, contained eight chapels arranged around a ninth, central chapel dedicated to the Intercession; a tenth chapel was erected in 1588 over the grave of the venerated local saint Vasily (Basil). In the 16th and 17th centuries, it was perceived as the earthly symbol of the Heavenly City. Like all churches in Byzantine Christianity, the church was popularly known as the "Jerusalem" and served as an allegory of the Jerusalem Temple in the annual Palm Sunday parade attended by the Patriarch of Moscow and the Tsar.

Tikhon of Moscow (Russian: Тихон Московский, 31 January [O.S. 19 January] 1865 – 7 April [O.S. 25 March] 1925), born Vasily Ivanovich Bellavin (Russian: Василий Иванович Беллавин), was a bishop of the Russian Orthodox Church (ROC). On 5 November 1917 (OS) he was selected the 11th Patriarch of Moscow and All Russia, after a period of about 200 years of the Synodal rule in the ROC. He was canonised as a confessor by the ROC in 1989.

The church reform of Peter the Great was a set of changes Peter I of Russia (r. 1682–1725) introduced to the Russian Orthodox Church, especially to church government. Issued in the context of Peter's overall Westernizing reform programme, it replaced the office of the patriarch of Moscow with the Holy Synod and made the church effectively a department of state.

Peter did not abandon Orthodoxy as the main ideological core of the state, but attempted to start a process of Westernization of the clergy, relying on those with a Western theological education.

Feodor Nikitich Romanov (Russian: Фео́дор Ники́тич Рома́нов, IPA: [ˈfʲɵdər nʲɪˈkʲitʲɪtɕ rɐˈmanəf]; 1553 – 1 October [O.S. 21 September] 1633) was a Russian boyar who after temporary disgrace rose to become patriarch of Moscow as Filaret (Russian: Филаре́т, IPA: [fʲɪɫɐˈrʲet]), and became de facto ruler of Russia during the reign of his son, Mikhail Feodorovich.

An epanokalimavkion (Greek: επανωκαλυμμαύχιον, also epanokalimavko (επανωκαλύμμαυχο)) is an item of clerical clothing worn by Orthodox Christian monastics who are rassophor or above, including bishops. It is a cloth veil, usually black, which is worn with a kalimavkion.