Castellans of the Polish–Lithuanian Commonwealth in the context of "Polish nobility"

The szlachta (Polish pronunciation: [ˈʂlaxta] ; Lithuanian: šlėkta; lit. 'nobility') , the nobles, were the noble estate of the realm in the Kingdom of Poland, the Grand Duchy of Lithuania, and the Polish–Lithuanian Commonwealth. It was the dominating social class in the Kingdom of Poland and the Polish-Lithuanian Commonwealth, which was exercising political rights and power. Szlachta as a class differed substantially from the feudal nobility of Western Europe. The estate was officially abolished in 1921 by the March Constitution.

The origins of the szlachta are obscure and the subject of several theories. The szlachta secured substantial and increasing political power and rights throughout its history, beginning with the reign of King Casimir III the Great between 1333 and 1370 in the Kingdom of Poland until the decline and end of the Polish–Lithuanian Commonwealth in the late 18th century. Apart from providing officers for the army, its chief civic obligations included electing the monarch and filling honorary and advisory roles at court that would later evolve into the upper legislative chamber, the Senate. The szlachta electorate also took part in the government of the Commonwealth via the lower legislative chamber of the Sejm (bicameral national parliament), composed of representatives elected at local sejmiks (local szlachta assemblies). Sejmiks performed various governmental functions at local levels, such as appointing officials and overseeing judicial and financial governance, including tax-raising. The szlachta assumed various governing positions, including voivode, marshal of voivodeship, castellan, and starosta.

The Union of Horodło or Pact of Horodło was a set of three acts signed in the town of Horodło on 2 October 1413. The first act was signed by Władysław II Jagiełło, King of Poland, and Vytautas, Grand Duke of Lithuania. The second and third acts were composed by the Polish nobility (szlachta) and Lithuanian boyars, respectively. The union amended the earlier Polish–Lithuanian unions of Krewo and Vilnius–Radom. Politically, Lithuania received more autonomy as, after the death of Vytautas, the Lithuanian nobles could choose another Grand Duke instead of passing the title to Władysław II Jagiełło or his heir. However, culturally, Lithuania and Poland grew closer. Lithuania adopted Polish institutions of castellans and voivodes. Catholic Lithuanian nobles and church officials were granted equal rights with the Polish nobles and clergy. Forty-seven selected Lithuanian nobles were adopted by Polish families and granted Polish coats of arms. Thus the union signified the beginnings of the Polonization of Lithuanian culture and the rise of the Lithuanian nobility. It was one of the major steps towards the modernization and Europeanization of Lithuania.