Mazurians

The Masurians or Mazurs (Polish: Mazurzy, German: Masuren, Masurian: Mazurÿ) are a small 5,000-15,000 strong Lechitic sub-ethnic group in the present-day Warmian-Masurian Voivodeship, Poland. Before World War II and its post-war expulsions, Masurians used to be a more numerous ethnic group found in the southern parts of East Prussia for centuries following the 16th century Protestant Reformation.

They are descended from Masovians (Polish: Mazowszanie; German: Masowier), who were Polish settlers from Mazovia. These settlers moved to the Duchy of Prussia during and after the Protestant Reformation. They spoke Masurian dialect. Since the middle 19th century, High German was increasingly used among Masurians as opposed to Low German used by most of East Prussia's German population. Many Masurians were often bilingual in German and Polish languages. In the 19th century, the Masuria region of East Prussia was named after the Masurians.

Like most of the East Prussian population, they favored Protestantism and adopted Lutheranism in 1525 when Albert, Duke of Prussia secularized the duchy and converted. Roman Catholic Warmiaks and Masovians were not affected as they inhabited parts that formally belonged to the Kingdom of Poland.