first independent metropolitan of Moscow, elected in 1448.

Until the 15th century the Orthodox Church had depended upon the patriarch of Constantinople to choose its ecclesiastical head, usually a Greek, to fill the position of metropolitan of Kiev (later metropolitan of Moscow). In 1448, however, the Russian Church (Russian Orthodox church) declared itself “autocephalous” (i.e., independent of Constantinople) as a result of the actions of the Byzantine-appointed metropolitan Isidore (Isidore Of Kiev), who accepted the decision of the Council of Florence in 1439 and embraced the idea of reuniting the Eastern Orthodox and Roman Catholic churches. Grand Prince Vasily (Basil) II of Russia arrested and imprisoned Isidore, and the council of Russian bishops elected Jonas as metropolitan, without Byzantine consent.

Jonas' appointment, an act of Russian national pride, marked the weakening of Constantinople's ecumenical primacy; and many, including Jonas, believed that when Constantinople eventually fell, as it did to the Turks in 1453, Moscow would become the new centre of Eastern Orthodoxy.