Born ar Wolczyn, son of a general, a clever young man admired in the Courts of Europe, he went to Russia where he became the lover of Catherine, wife of the czarevich Peter.

Back to Poland in 1758 he was elected king in 1764 with the help of the Russian Czar.

He was a "confirmed bachelor".

It seems that his lover was the British Major General Charles Lee, a soldier of fortune in the Polish army (there are some hints in their correspondence that they may have had an homosexual relationship).

During an insurrection he was deprived of all real power, and in 1795 he renounced the throne, being thus the last king of Poland.

He moved to Russia again, and there he died, three years later, in St. Petersburg.