The subject of the paper is the concept of natural law in the teachings of Martin Luther (1483- 1546) and its relationship with the ideological shaping of the Duchy of Prussia during the reign of Duke Albrecht von Brandenburg-Ansbach (1525-1568). Martin Luther’s theological teachings recognised the concept of the reality of two states, divine and temporal, reflecting the divine natural order. In this order, the principles of natural law were the fundamental regulator of the position of humans and society, but also of the notion of state power, understood as a divine tool in shaping the temporal existence of people on the way to salvation or damnation. Luther’s teachings fundamentally influenced the political and religious thinking of Duke Albrecht von Brandenburg-Ansbach, the first secular ruler of the Duchy of Prussia. Albrecht’s behaviour, who personally became invested in Luther’s views, led to the formation of the principality and the Prussian Church as two interconnected elements over which the duke, who was the divine vicar, exercised both secular and spiritual power, directly reflecting the principles of the teaching of the German reformer. Translated by Aleksander Pluskowsk