The Ruthenian nobility (Ukrainian: Руська шляхта, romanized: Ruska shlyakhta; Belarusian: Руская шляхта, romanized: Ruskaja šlachta; Polish: szlachta ruska) originated in the territories of Kievan Rus' and Galicia–Volhynia, which were incorporated into the Grand Duchy of Lithuania, Polish–Lithuanian Commonwealth and later the Russian and Austrian Empires. The Ruthenian nobility became increasingly Polonized and later Russified, while retaining a separate cultural identity.
The Ruthenian nobility, originally characterized as East Slavic-speaking and Eastern Orthodox, found itself ruled by the expanding Grand Duchy of Lithuania, where it rose from second class status to equal partners of the Lithuanian nobility. Following the Polish–Lithuanian union of the 14th century, the Ruthenian nobles became increasingly Polonized, adopting the Polish language and religion (which increasingly meant converting from the Orthodox faith to Roman Catholicism). Ruthenian nobility, however, retained a distinct identity within the body of the Polish-Lithuanian szlachta, leading to the Latin expression gente Ruthenus, natione Polonus or gente Rutheni, natione Poloni (translated as "of Polish nationality, but Ruthenian origin", "of Ruthenia race and Polish nation", or in various similar veins), although the extent to which they retained and maintained this separate identity is still debated by scholars, and varied based on time and place.
