Old Believers or Old Ritualists are Eastern Orthodox Christians who maintain the liturgical and ritual practices of the Russian Orthodox Church as they were before the reforms of Patriarch Nikon of Moscow between 1652 and 1666. Resisting the accommodation of Russian piety to the contemporary forms of Greek Orthodox worship, these Christians were anathematized, together with their ritual, in a Synod of 1666–67, producing a division in Eastern Europe between the Old Believers and those who followed the state church in its condemnation of the Old Rite. Russian speakers refer to the schism itself as raskol (раскол), etymologically indicating a "cleaving-apart".

Nikon, born Nikita Minin was the seventh Patriarch of Moscow and all Rus' of the Russian Orthodox Church, serving officially from 1652 to 1666. He was renowned for his eloquence, energy, piety and close ties to Tsar Alexis of Russia. Nikon introduced many reforms, including liturgical reforms that were unpopular among conservatives. These divisions eventually led to a lasting schism known as Raskol (schism) in the Russian Orthodox Church. For many years, he was a dominant political figure, often equaling or even overshadowing the Tsar. In December 1667, Nikon was tried by a synod of church officials, deprived of all his sacerdotal functions, and reduced to the status of a simple monk.