Edinoverie (Russian: Единове́рие; IPA: [jɪdʲɪnɐˈvʲerʲɪjɪ], literally coreligionism) is an arrangement between certain Russian Old Believer communities and the official Russian Orthodox Church, whereby the communities are treated as a part of the normative Orthodox Church system, while maintaining their own traditional rites. Thus, they are often described as Old-Ritualists (Russian: Старообря́дцы, Staroöbriadtsy), rather than Old Believers.
The Russian word Edinoverie may be a back-formation of Edinovertsy (единоверцы; sometimes also transcribed Yedinovertsy), i.e. 'coreligionists' (literally, 'one's of the same faith'; the word is also used to refer to members of Edinoverie community). It may be interpreted as 'Unity in Faith', although perhaps a more precise meaning would be "Accepting [the Old-Rite Christians] as people of the same faith [by the Established Church]". More open-minded hierarchs of the State Church saw in the Edinoverie a mutual acceptance. In the words of Filaret, Metropolitan of Moscow, addressed to the Edinovertsy at the consecration of St Nicholas Church for them at Rogozhskoye Cemetery (1854), «Вы единоверцы нам, а мы единоверцы вам» ("You are people of our faith, and we are people of your faith").
Edinoverie arrangements began to appear in the last quarter of the 18th century, after more than a century of struggle between Russia's established Orthodox Church and various Old Believer groups, who did not recognise the changes to the church rituals and the official translations of the Scripture made under the leadership of Patriarch Nikon in the 1660s.
On the side of the established church, the initiators of Edinoverie are said to be Metropolitan Platon of Moscow (the senior hierarch of the Russian Orthodox Church) and Archbishop Nikifor, who was Archbishop first of Sloviansk and Kherson, and later of Astrakhan and Stavropol in South Russia.