Synod of Lviv (1946)

The Synod of Lviv or the Council of Lviv (Ukrainian: Львівський собор, romanized: Lvivskyi sobor; Russian: Львовский собор, romanized: Lvovsky sobor) was a March 1946 synod of the Ukrainian Greek Catholic Church that declared the 1596 Union of Brest to be annulled, thereby unifying the church with the Russian Orthodox Church. Held amidst a climate of repression by the Soviet government, the synod was rejected by the majority of the church's adherents, leading them to continue their practices underground until their activity was again legalised under Mikhail Gorbachev's policy of Glasnost.

The Soviet government had begun plans to forcibly dismantle the UGCC following their invasion of eastern Poland (present-day western Ukraine), although they were put on hold due to, among other reasons, Operation Barbarossa. With the region's recapture in 1944, the process was soon restarted in response to the UGCC's support for anti-communist Ukrainian nationalists, and the church's leadership was arrested. An organisation of three Catholic priests known as the Sponsoring Group was created in May 1945, and, with the support of the NKGB and Russian Orthodox Church, successfully pushed for the unification of the UGCC into the Russian Orthodox Church. The process was formalised by a March 1946 synod. As a result of the synod, the UGCC became the largest illegal religious organisation in the world, and followers were subject to persecution for over forty years until they were permitted to practice their faith in 1989, after a long-running campaign by Ukrainian Soviet dissidents.