Transylvania, an Ottoman vassal state, functioned for many years as an independent country. In 1542 Martinuzzi revived the 1437 Union of Three Nations to govern the land, and the Transylvanian nobles regularly met in their own Diet. In 1572 the Diet created freedom of worship and equal political rights for members of Transylvania's four "established" religions: Roman Catholic, Lutheran, Unitarian, and Calvinist. The Eastern Orthodox Romanian serfs were permitted to worship, but the Orthodox Church was not recognized as an "established" religion, and the Romanians did not share political equality.

In 1591 the Habsburgs invaded Transylvania under George Basta, who persecuted Protestants and expropriated estates illegally until Istvan Bocskay, a former Habsburg supporter, mustered an army that expelled Basta's forces in 1604-05. In 1606 Bocskay concluded the Peace of Vienna with the Habsburgs and the Peace of Zsitvatorok with the Turks. The treaties secured his position as prince of Transylvania, guaranteed rights for Royal Hungary's Protestants, broadened Transylvania's independence, and freed the emperor of his obligation to pay tribute to the Ottomans. After Bocskay's death, the Ottomans compelled the Transylvanians to accept Gabor Bethlen as prince. Transylvania prospered under Bethlen's enlightened despotism. He stimulated agriculture, trade, and industry sank new mines sent students to Protestant universities abroad and prohibited landlords from barring children of serfs from an education. Unfortunately, when Bethlen died in 1629, the Transylvanian Diet abolished most of his reforms. After a short succession struggle, Gyorgy Rakoczi I (1648-60) became prince. Under Rakoczi, Transylvania fought with the Protestants in the Thirty Years' War (1618-48) and was mentioned as a sovereign state in the Peace of Westphalia. Transylvania's golden age ended after Gyorgy Rakoczi II (1648-60) launched an attack on Poland without the prior approval of the Ottomans or Transylvania's Diet. The campaign was a disaster, and the Turks used the opportunity to rout Rakoczi's army and take control of Transylvania.

Data as of September 1989