Polish–Lithuanian Commonwealth

The Polish–Lithuanian Commonwealth was a union of Poland and Lithuania which controlled much of Eastern Central Europe from 1569 to 1795.

Its predecessors, the kingdom of Poland and the Grand Duchy of Lithuania, had centuries of history beforehand. Poland–Lithuania was a beacon for liberty in a time when absolute monarchy was the norm in Europe. The union was known for religious tolerance, ethnic diversity, and parliamentary rule. While formally called a Res Publica in Latin (Rzeczpospolita in Polish and Respublika in Lithuanian), it was not a republic in the modern sense, but had a unique form of government: The head of state was simultaneously King of Poland, Grand Duke of Lithuania and President of the Republic. He was elected for life by the numerous members of the aristocracy and gentry (Szlachta) who made up more than 10 percent of the total population (much more than in other European countries of that time). The elected monarchs came either from the Polish high nobility (magnates) or from foreign dynasties like the Swedish House of Vasa and later the Electors of Saxony who reigned both countries in personal union for much of the 18th century (the "Saxon era"). Bribes often decided who was elected king. The powers of the respective monarch were very limited, while the nobles enjoyed "Golden Liberty". Each member of parliament (Sejm) had a veto right, making decisions very difficult.

At the end of the 18th century, the country was partitioned between three rising great powers; the Russian Empire, the Austro-Hungarian Empire and Prussia (later the German Empire) throughout the 19th century. Poland and Lithuania were devastated in the crossfire of two world wars, were subjugated to the Soviet Union, and achieved functional independence only with the 1980s revolutions. However, Polish-Lithuanian rule was instrumental in the formation of separate Ukrainian and Belarusian national identities from Russia, and the formation of distinct Ukrainian and Belarusian languages.

Ukraine
Due to its history as part of the Polish-Lithuanian Commonwealth and later, the Austro-Hungarian Empire, the westernmost part of Ukraine has a Catholic majority, in contrast to the rest of majority-Eastern Orthodox Ukraine.