The chief religion of Russia is Russian Orthodox Christianity, which is professed by about 75 percent of citizens who describe themselves as religious believers. Because the concept of separation of church and state never took root in Russia, the Russian Orthodox Church, a branch of Eastern Orthodoxy, was a pillar of tsarist autocracy. During the communist era, the church, like every other institution in the Soviet Union, was completely subordinate to the state, achieving a modus vivendi by ceding most of its autonomous identity. Under the officially atheist regimes of the Soviet Union, no official figures on the number of religious believers in the country were available to Western scholars. According to various Soviet and Western sources, however, more than one-third of the citizens of the Soviet Union regarded themselves as believers in the 1980s, when the number of adherents to Russian Orthodoxy was estimated at more than 50 million--although a high percentage of that number feared to express their religious beliefs openly.
Islam, professed by about 19 percent of believers in the mid-1990s, is numerically the second most important religion in Russia. Various non-Orthodox Christian denominations and a dwindling but still important Jewish population complete the list of major religious groups in the Russian Federation. In general, Russians of all religions have enjoyed freedom of worship since the collapse of the communist regime in 1991, and large numbers of abandoned or converted religious buildings have been returned to active religious use in the 1990s.