The szlachta ([ˈʂlaxta], exonym: Nobility) was a legally privileged noble class in the Kingdom of Poland, Grand Duchy of Lithuania, Ruthenia, Samogitia (both after Union of Lublin became a single state, the Polish–Lithuanian Commonwealth) and the Zaporozhian Host. It originated and gained considerable institutional privileges between 1333 and 1370 in Kingdom of Poland during the reign of King Casimir III the Great. In 1413, following a series of tentative personal unions between the Grand Duchy of Lithuania and the Crown Kingdom of Poland, the existing Lithuanian-Ruthenian nobility formally joined this class. As the Polish-Lithuanian Commonwealth (1569–1795) evolved and expanded in territory, its membership grew to include the leaders of Ducal Prussia and Livonia.
The origins of the szlachta are shrouded in obscurity and mystery and have been the subject of a variety of theories. Traditionally, its members were owners of landed property, often in the form of "manor farms" or so-called folwarks. The nobility negotiated substantial and increasing political and legal privileges for itself throughout its entire history until the decline of the Polish–Lithuanian Commonwealth in the late 18th century.