Maria was on a list of 99 eligible European princesses to marry the young king.
Cardinal Fleury, who wanted for the king a royal bride who would not drag France into any complicated political alliances, supported the marriage. One aspect in the choice of Marie was the fact that she was old enough to have children, while the former designated bride, the Infanta Mariana Victoria of Spain, was too young to bear children.
The marriage by proxy took place on 15 August 1725 in the cathedral of Strasbourg, Louis XV being represented by his cousin the Duke of Orléans, Louis le Pieux.
Louis and Marie first met on the eve of their wedding, which took place on 5 September 1725, at the Château de Fontainebleau. Marie was twenty-two years old and Louis fifteen. The young couple was reported to have fallen in love at first sight.
The announcement of the wedding was not received well as the royal court, who considered the match to be a misalliance, as the father of Marie had been a monarch for such a short time. There were rumours before the wedding that the bride was ugly, epileptic and sterile. However, Marie earned popularity among the population from the beginning, when she handed out money on her way to her wedding in Fontainebleau.
Cardinal de Fleury, who had been Louis' tutor, was appointed Grand Chaplain to Marie.
Upon her marriage, Maria's Polish name was modified into French as Marie Leczinska.
The young couple's marriage was initially happy. In August 1727, Maria gave birth to her first children, twin daughters named Louise Élisabeth de France and Henriette Anne de France, at the Palace of Versailles. The elder twin, Louise Élisabeth, later married the Infante Felipe of Spain and eventually became the Duchess Consort of Parma. Through Louise Élisabeth, Marie became an ancestor of Juan Carlos I of Spain.
After the difficult birth of Louise Marie de France, in 1737, which nearly took her life, she had no more children. In 1738, she refused Louis entrance to her bedroom, and after this, their private relationship ended, though the formal marriage continued in spite of her husband's infidelities.
Louis's marriage to Marie Leszczyńska produced many children, but the king was persistently (and notoriously) unfaithful.
* Louise Élisabeth (14 August 1727 – 6 December 1759) Duchess of Parma, had issue;
* Henriette (14 August 1727 – 10 February 1752) died unmarried.
* Marie Louise (28 July 1728 – 19 February 1733) died in childhood:
* Louis, Dauphin of France (4 September 1729 – 20 December 1765) married Infanta Maria Teresa Rafaela of Spain; had issue then married Duchess Marie-Josèphe of Saxony and had issue;
* Philippe of France, Duke of Anjou (30 August 1730 – 17 April 1733) died in childhood
* Adélaïde (23 March 1732 – 27 February 1800) died unmarried
* Victoire (11 May 1733 – 7 June 1799) died unmarried
* Sophie (17 July 1734 – 3 March 1782); died unmarried
* Stillborn Child (28 March 1735 – 28 March 1735)
* Thérèse (16 May 1736 – 28 September 1744) died in childhood
* Louise Marie (5 July 1737 – 23 December 1787) was a nun
Most of her husband's romantic affairs were with her knowledge, and she either simply accepted them, or was powerless to stop them, and throughout, she displayed an attitude of discretion and dignity. She upheld a relatively good relationship toward Madame de Pompadour.
Marie had a very close relationship to her children.
Marie died at Versailles on 24 June 1768, six years before her husband.