Born into wealthy Polish aristocracy, Poniatowski arrived as a diplomat at the Russian imperial court in Saint Petersburg in 1755 at the age of 22[1] and became intimately involved with the future empress Catherine the Great.

With her aid, he was elected King of Poland and Grand Duke of Lithuania by the Sejm in September 1764[2][3][4] following the death of Augustus III.

Stripped of all meaningful power, Poniatowski abdicated in November 1795 and spent the last years of his life as a captive in Saint Petersburg's Marble Palace.

A controversial figure in Poland's history, he is viewed with ambivalence as a brave and skillful statesman by some and as an overly hesitant coward by others, and even as a traitor.

He is criticized primarily for his failure to resolutely stand against opposing forces and prevent the partitions, which led to the destruction of the Polish state.

Historians tend to agree that, taking the circumstances into account, he was a skillful statesman, pointing out that passing the Constitution was a sign of bravery, although his unwillingness to organize a proper nationwide uprising afterward is seen as cowardice and the key reason for the Second Partition and the subsequent downfall of Poland.

He was one of eight surviving children, and the fourth son, of Princess Konstancja Czartoryska and of Count Stanisław Poniatowski, Ciołek coat of arms, Castellan of Kraków.

[5][6] He was a great-grandson of poet and courtier Jan Andrzej Morsztyn and of Lady Catherine Gordon, lady-in-waiting to Queen Marie Louise Gonzaga; thus descended from the Marquesses of Huntly and the Scottish nobility.

He was temporarily kidnapped as a toddler, on the orders of Józef Potocki, Governor of Kiev, as a reprisal for his father's support for King Augustus III and held for some months in Kamieniec-Podolski.

[6] He went on his first foreign trip in 1748, with elements of the Imperial Russian army as it advanced into the Rhineland to aid Maria Theresia's troops during the War of the Austrian Succession which ended with the Treaty of Aix-la-Chapelle (1748).

[10] Later that year, after serving at the Radom Tribunal and meeting King Augustus III of Poland, he was elected deputy of the Sejm (Polish parliament).

[10] He returned to the Commonwealth later that year, however he eschewed the Sejm, as his parents wanted to keep him out of the political furore surrounding the Ostrogski family's land inheritance (see: fee tail – Ordynacja Ostrogska).

[23][24] Together with the Familia he tried to reform the ineffective system of government, by reducing the powers of the hetmans (Commonwealth's top military commanders) and treasurers, moving them to commissions elected by the Sejm and accountable to the King.

The growing rift between Poniatowski and the Familia was exploited by the Russians, who used the issue as a pretext to intervene in the Commonwealth's internal politics and to destabilize the country.

[25] After an unsuccessful attempt to raise allies in Western Europe, France, Britain and Austria, Poniatowski and the Familia had no choice but to rely more heavily on the Russian Empire, which treated Poland as a protectorate.

[30][31] In view of the continuing weakness of the Polish-Lithuanian state, Austria, Russia, and Prussia collaborated to threaten military intervention in exchange for substantial territorial concessions from the Commonwealth – a decision they made without consulting Poniatowski or any other Polish parties.

[34] Royal prerogative was restricted, so that the King lost the power to confer titular roles, and military promotions, to appoint ministers and senators.

[34][36][37] The Sejm also created two notable institutions: the Permanent Council, a government body in continuous operation, and the Commission of National Education.

"[48] According to a contemporary account, Poniatowski himself described it, as "founded principally on those of England and the United States of America, but avoiding the faults and errors of both, and adapted as much as possible to the local and particular circumstances of the country.

[52] The contacts of Polish reformers with the revolutionary French National Assembly were seen by Poland's neighbours as evidence of a conspiracy and a threat to their absolute monarchies.

[52] Russia's wars with the Ottomans and Sweden having ended, Catherine was furious over the adoption of the Constitution, which threatened Russian influence in Poland.

[56][57][58] One of Russia's chief foreign policy authors, Alexander Bezborodko, upon learning of the Constitution, commented that "the worst possible news have arrived from Warsaw: the Polish king has become almost sovereign.

"[55] Shortly thereafter, conservative Polish nobility formed the Targowica Confederation to overthrow the Constitution, which they saw as a threat to the traditional freedoms and privileges they enjoyed.

[62] This army, under the command of the King's nephew Józef Poniatowski and Tadeusz Kościuszko, managed to defeat the Russians or fight them to a draw on several occasions.

Many reform leaders, believing their cause lost, went into self-exile, although they hoped that Poniatowski would be able to negotiate an acceptable compromise with the Russians, as he had done in the past.

[75] In 1990, due to the poor state of the Wołczyn church (then in the Byelorussian SSR), his body was once more exhumed and was brought to Poland, to St. John's Cathedral in Warsaw, where on 3 May 1791 he had celebrated the adoption of the Constitution that he had coauthored.

[84][85] According to a 1795 inventory, Stanisław August's art collection, spread among numerous buildings, contained 2,889 pieces, including works by Rembrandt, Rubens, and van Dyck.

[68][91] In Polish historiography and in popular works, he has been criticized or marginalized by authors such as, Szymon Askenazy, Joachim Lelewel, Jerzy Łojek (whom Andrzej Zahorski describes as Poniatowski's most vocal critic among modern historians), Tadeusz Korzon, Karol Zyszewski and Krystyna Zienkowska; whereas more neutral or positive views have been expressed by Paweł Jasienica, Walerian Kalinka, Władysław Konopczyński, Stanisław Mackiewicz, Emanuel Rostworowski and Stanisław Wasylewski.

[75] Andrzej Zahorski dedicated a book to a discussion of Poniatowski, The Dispute over Stanisław August (Spór o Stanisława Augusta, Warsaw, 1988).

However, according to Wirydianna Fiszerowa, a contemporary who knew them both, this rumour only spread after the death of Poniatowski, was generally disbelieved, and moreover, was circulated by Elżbieta herself, so the marriage is considered by most to be unlikely.