Who was the last monarch of the Polish–Lithuanian Commonwealth?

Stanisław II Augustus (born Stanisław Antoni Poniatowski; 17 January 1732 – 12 February 1798), who reigned as King of Poland and Grand Duke of Lithuania from 1764 to 1795, was the last monarch of the Polish–Lithuanian Commonwealth. He remains a controversial figure in Polish history. Recognized as a great patron of the arts and sciences and an initiator and firm supporter of progressive reforms, he is also remembered as the King of the Commonwealth whose election was marred by Russian intervention. He is criticized primarily for his failure to stand against the partitions, and thus to prevent the destruction of the Polish state.

Having arrived at the Russian imperial court in Saint Petersburg in 1755, he became romantically involved with the future empress Catherine the Great (from 1762 to 1796). With her connivance, in 1764 he was elected King of Poland. Contrary to expectations, he attempted to reform and strengthen the ailing Commonwealth. His efforts met with external opposition from Prussia, Russia and Austria, all committed to keeping the Commonwealth weak. From within he was opposed by conservative interests, which saw reforms as threatening their traditional liberties and privileges.