The Polish-Lithuanian Commonwealth, also known as the First Polish Republic or Republic (Commonwealth) of the Two (Both) Nations (Peoples), ( or Rzeczpospolita Obojga Narodów; ) or as the "First Republic," was one of the largest and most populous countries in
17th-century Europe. Its political structure — that of a semi-federal, semi-confederal
aristocratic republic — was formed in 1569 by the
Union of Lublin, which united the
Kingdom of Poland and the
Grand Duchy of Lithuania, and lasted in this form until the adoption of the
Constitution of May 3, 1791. The Commonwealth covered not only the territories of what is now
Poland and
Lithuania, but also the entire territory of
Belarus and
Latvia, large parts of
Ukraine and
Estonia, and part of present-day western
Russia (
Smolensk and
Kaliningrad oblasts). Originally the official languages of the Commonwealth were
Polish and
Latin (in the Kingdom of Poland) and
Ruthenian and
Lithuanian (in the Grand Duchy of Lithuania).
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