2018 Moscow–Constantinople schism

A schism between the Russian Orthodox Church (ROC, also known as the Moscow Patriarchate) and the Ecumenical Patriarchate of Constantinople 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.

In its decision of 15 October 2018, the Holy Synod of the Russian Orthodox Church barred all members of the Moscow Patriarchate (both clergy and laity) from taking part in communion, baptism, and marriage at any church controlled by the Ecumenical Patriarchate. Before that, in response to the appointment of two exarchs of the Ecumenical Patriarchate in Ukraine, the Holy Synod of the Moscow Patriarchate had decided, on 14 September 2018, to break off participation in any episcopal assemblies, theological discussions, multilateral commissions, and any other structures that are chaired or co-chaired by representatives of the Ecumenical Patriarchate.

The schism forms part of a wider political conflict involving Russia's 2014 annexation of Crimea and its military intervention in Ukraine, as well as Ukraine's subsequent desire to join the European Union and NATO. This schism is reminiscent of the Moscow–Constantinople schism of 1996 over canonical jurisdiction over Estonia, which was however resolved after less than three months.

On 21 October 2019, Archbishop Ieronymos II of Athens, the primate of the Church of Greece, sent a peaceful letter to Epiphanius, the primate of the Orthodox Church of Ukraine (OCU, that was formed by the unification of the UOC-KP, UAOC, and parts of the UOC-MP on 15 December 2018). This decision was supported by the whole hierarchy (bishops) of the Church of Greece, minus seven metropolitans. This decision meant that the Church of Greece recognized the OCU. The ROC had announced previously it would break communion with any hierarch of the Church of Greece who enters in communion with any hierarch of the OCU. On Sunday, 3 November 2019, Patriarch Kirill of Moscow did not mention the primate of the Church of Greece in the liturgy, removing him from the diptych. On 26 December, the ROC broke eucharistic communion with the Greek Orthodox patriarch of Alexandria, Theodore II, and ceased commemorating him, because he had recognized the OCU the month before. On 20 November 2020, the Holy Synod of the ROC declared that Patriarch Kirill can no longer commemorate Archbishop Chrysostomos II of Cyprus as a result of Chrysostomos' commemoration of Epiphanius on 24 October 2020.

On 22 November 2022, the Patriarch of Alexandria Theodore II stopped the commemoration of Patriarch Kirill of Moscow.