Marie Casimire Louise de La Grange d'Arquien (Polish: Maria Kazimiera Ludwika d’Arquien, Lithuanian: Marija Kazimiera; 28 June 1641 – 30 January 1716), known also by the diminutive form "Marysieńka", was a French noblewoman who became the queen consort of Poland and Grand Duchess consort of Lithuania from 1674 to 1696 by her marriage to King and Grand Duke John III Sobieski of the Polish–Lithuanian Commonwealth. She had great influence upon the affairs of state with the approval of her spouse, and acted in effect as regent during his absence.
Marie Casimire and her sister Louise Marie were the only surviving children of Henri de la Grange, Marquis d'Arquien and his first wife, Françoise de la Chastre (1613–1648). She came to Poland at the age of five years as a lady in waiting to Marie Louise Gonzaga, the French-born Queen of Poland and Grand Duchess of Lithuania from 1645 to 1672, wife and consort to two Polish kings and Lithuanian grand dukes — Władysław IV Vasa and later his brother (who succeeded him) John II Casimir Vasa. Marie Louise was rumored to be Marie Casimire's real mother, although unproven, they certainly had a close relationship. The harsh climate of Poland did not prove healthy for Marie Casimire, and she developed a persistent cough and recurring fever.
At the court, she met and fell in love with Jan Sobieski, who arrived in 1656, but she was first married off to Jan "Sobiepan" Zamoyski in 1658, with whom she had four children, all of whom died in early childhood. Jan Zamoyski died on 2 April 1665 and the widowed Marie Casimire married Jan Sobieski just over three months later, on 14 July of the same year. The couple had thirteen children together, but only four of them reached adulthood — Jakub, Aleksander, Konstanty and Teresa (who later became Kurfürstin of Bavaria and mother to Emperor Karl VII).
Queen of Poland and Grand Duchess of Lithuania
John Sobieski was elected King of Poland and Grand Duke of Lithuania in 1674, not without the influence of his wife. As the Queen of Poland and Grand Duchess of Lithuania, Marie Casimire quickly became unpopular, as she supported the proposed Polish–French alliance, while simultaneously striving to gain privileges for her family from the French King Louis XIV, whom she greatly admired. Like Marie Louise Gonzaga, Marie Casimire was a strong supporter of an absolute monarchy, for which she was reviled by certain spheres of the Szlachta. The nobility were scandalised at the queen's political meddling, believing that foreign women shouldn't interfere with politics. Marie Casimire also opposed the Commonwealth's policy of religious toleration and supported the Edict of Fontainebleau of 1685.
Her influence is exemplified in an incident in 1678, when the Chancellor of Nowogrod, Mikołaj Władysław Przeździecki, came to the king as the leader of an unofficial delegation to present him with evidence that the Pac family were his enemies. According to Mikolaj Wladyslaw Prze Dziecki, "The Queen knocked on the doors until the King asked for them to be opened and then took the monarch by the hand, leading him to the side, with great force, speaking in French", which the Chancellor viewed with disgust.
In the 1670s, the king of France wished to close a treaty between France, Sweden, the Polish-Lithuanian Commonwealth and the Ottoman Empire. The French ambassador recommended working with Marie Casimire since "only the Queen Consort of Poland can convince the King, her husband, to close a treaty".
Queen Marie Casimire gave her support to this issue, and a secret treaty was signed in Jaworowo on 11 June 1675, and completed by a treaty between Poland and Sweden in 1677.
Her Pro-French policies were, however, discontinued in 1678, when France had not fulfilled the terms promised her for her services, such as making her father a Peer of France, combined with the fact that Marie Casimire became more concerned with the threat of the Turks.
Queen Marie Casimire sent her lady-in-waiting and confidante Malgorzata Korowska as her political agent to the Emperor Leopold I in 1679 to find out his view concerning an alliance between the emperor and Poland against Turkey. On 1 April 1683, Poland signed the military alliance with the emperor, which she had supported.
She also played an important role during the war against Turkey, when she was credited with having convinced her spouse to support the emperor when Vienna was attacked in 1683. The French ambassador Michelle de Mongrillon described her influence when he commented:
"She could move her husband first of all, then she moved the huge, lethargic corps of the Commonwealth that is so difficult to set in motion".
Poland and Lithuania joined the Holy League in 1684, an act which had been promoted by Marie Casimire.
When King John Sobieski was absent in Wallachia and Moldova in 1686 and 1691 and at the Battle of Kamenets, Marie Casimire is acknowledged to have ruled in effect as regent in his absence.
As such, she had the authority to negotiate the military and trade treaty with France in September 1692, which restored the relations between Paris, Copenhagen, Stockholm and Warsaw, known as the "Crown of the North Alliance". She worked with the French ambassador Robert Le Roux d'Esenval and his successor Melchior de Polignac to settle unsettled affairs within the Crown of the North Alliance as well as the peace treaty with Turkey.
In 1695, she successfully solved the conflict between the King's supporter, the Bishop of Vilnius, Konstanty Brzostowski, and Kazimierz Jan Sapieha, as she wished to win the Sapieha party to support her son's candidacy as king and grand duke.
Queen Marie Casimire herself commented concerning the great political influence she had during the reign of her spouse in a letter in retrospect:
"I bear the burden of all the matters at hand, as my late husband loved me more than I deserved. Therefore, he did anything that pleased me and that I allowed for, as he considered me smarter than I am".