The Russian Orthodox Church (ROC; Russian: Русская православная церковь, РПЦ, romanized: Russkaya pravoslavnaya tserkov, RPTs;), also officially known as the Moscow Patriarchate (Russian: Московский патриархат, romanized: Moskovskiy patriarkhat), is an autocephalous Eastern Orthodox Christian church. It has 194 dioceses inside Russia. The primate of the ROC is the patriarch of Moscow and all Rus'.

The history of the ROC begins with the Christianization of Kievan Rus', which commenced in 988 with the baptism of Vladimir the Great and his subjects by the clergy of the ecumenical patriarch of Constantinople. Starting in the 14th century, Moscow served as the primary residence of the Russian metropolitan. The ROC declared autocephaly in 1448 when it elected its own metropolitan. In 1589, the metropolitan was elevated to the position of patriarch with the consent of Constantinople. In the mid-17th century, a series of reforms led to a schism in the Russian Church, as the Old Believers opposed the changes.

The ROC currently claims exclusive jurisdiction over the Eastern Orthodox Christians, irrespective of their ethnic background, who reside in the former member republics of the Soviet Union, excluding Georgia. The ROC also created the autonomous Church of Japan and Chinese Orthodox Church. The ROC eparchies in Belarus and Latvia, since the fall of the Soviet Union in the 1990s, enjoy various degrees of self-government, albeit short of the status of formal ecclesiastical autonomy.

The ROC should also not be confused with the Russian Orthodox Church Outside of Russia (or ROCOR, also known as the Russian Orthodox Church Abroad), headquartered in the United States. The ROCOR was instituted in the 1920s by Russian communities outside the Soviet Union, which had refused to recognise the authority of the Moscow Patriarchate that was de facto headed by Metropolitan Sergius Stragorodsky. The two churches reconciled on 17 May 2007; the ROCOR is now a self-governing part of the Russian Orthodox Church.

One of the foundational narratives associated with the history of Orthodoxy in Russia is found in the 12th-century Primary Chronicle, which says that the Apostle Andrew visited Scythia and Greek colonies along the northern coast of the Black Sea before making his way to Chersonesus in Crimea. According to the legend, Andrew reached the future location of Kiev and foretold the foundation of a great Christian city with many churches. Then, "he came to the [land of the] Slovenians where Novgorod now [stands]" and observed the locals, before eventually arriving in Rome. Despite the lack of historical evidence supporting this narrative, modern church historians in Russia have often incorporated this tale into their studies.

In the 10th century, Christianity began to take root in Kievan Rus'. Towards the end of the reign of Igor, Christians are mentioned among the Varangians. In the text about the treaty with the Byzantine Empire in 944–945, the chronicler also records the oath-taking ceremony that took place in Constantinople for Igor's envoys as well as the equivalent ceremony that took place in Kiev. Igor's wife Olga was baptized sometime in the mid-10th century; however, scholars have disputed the exact year and place of her conversion, with dates ranging from 946 to 960. Most scholars tend to agree that she was baptized in Constantinople, though some argue that her conversion took place in Kiev. Olga's son Sviatoslav opposed conversion, despite persuasion from his mother, and there is little information about Christianity in sources in the period between 969 and 988.

Ten years after seizing power, Grand Prince Vladimir was baptized in 988 and began Christianizing his people upon his return. That year was decreed by the Russian Orthodox Church in 1988 as the date of the Christianization of the country. According to the Chronicle, Vladimir had previously sent envoys to investigate the different faiths. After receiving glowing reports about Constantinople, he captured Chersonesus in Crimea and demanded that the sister of Basil II be sent there. The marriage took place on the condition that Vladimir would be also baptized there. Vladimir had lent considerable military support to the Byzantine emperor and may have besieged the city due to it having sided with the rebellious Bardas Phokas. By the early 11th century, Christianity was established as the state religion. By the early 13th century, some 40 episcopal sees had been established, all of which ultimately answered to Constantinople.

After Kiev lost its significance following the Mongol invasions, Metropolitan Maximus moved his seat to Vladimir in 1299. His successor, Peter, found himself caught in the conflict between the principalities of Tver and Moscow for supremacy in northwest Russia. Peter moved his residence to Moscow in 1325 and became a strong ally of the prince of Moscow. During Peter's tenure in Moscow, the foundation for the Dormition Cathedral was laid and Peter was buried there. By choosing to reside and be buried in Moscow, Peter had designated Moscow as the future center of the Russian Orthodox Church.