Royal Prussia
Royal Prussia was established after the Second Peace of Thorn (1466), from territory in western Prussia which had previously been part of the State of the Teutonic Order. It became a 'protectorate' of Poland. As such, it was not part of Poland proper, but feudal overlord status lay to the Polish king, reflected in the title "Royal Prussia" or the King's Prussia. Royal Prussia retained its autonomy, governing itself and maintaining its own laws, customs, rights and German language. As a royal protectorate, its magnates could participate in the election of its titular monarch, however it could not participate in the Sejm, the Polish parliament.