Albert of Prussia was a German nobleman who was the 37th Grand Master of the Teutonic Knights, who after converting to Lutheranism, became the first ruler of the Duchy of Prussia, the secularized state that emerged from the former Monastic State of the Teutonic Knights. Albert was the first European ruler to establish Lutheranism, and thus Protestantism, as the official state religion of his lands. He proved instrumental in the political spread of Protestantism in its early stage, ruling the Prussian lands for nearly six decades.
A member of the Brandenburg-Ansbach branch of the House of Hohenzollern, Albert became Grand Master, where his skill in political administration and leadership ultimately succeeded in reversing the decline of the Teutonic Order. But Albert, who was sympathetic to the demands of Martin Luther, rebelled against the Roman Catholic Church and the Holy Roman Empire by converting the Teutonic state into a Protestant and hereditary realm, the Duchy of Prussia, for which he paid homage to his uncle, Sigismund I, King of Poland. That arrangement was confirmed by the Treaty of Kraków in 1525.