In 1764, Stanisław II Augustus became the last king of which country?

Stanisław II Augustus (also Stanisław August Poniatowski; born Stanisław Antoni Poniatowski; 17 January 1732 – 12 February 1798) was the last King of Poland, Grand Duke of Lithuania and the last monarch of the united Polish–Lithuanian Commonwealth (1764–95). 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 last king of the Commonwealth whose election was marred by Russian involvement. He is criticized primarily for his failure to stand against the partitions, and thus to prevent the destruction of Poland.