Maria Clementina Sobieski (in Polish Maria Klementyna Sobieska), (1702-1735), Polish princess who was born on July 18, 1702 in Poland, the daughter of Poland’s Crown Prince James Louis Henry Sobieski, (1667-1737), and Hedwig Elisabeth Amelia de Baviere Pfalz-Neuburg, (1673-1722).

The granddaughter of John III Sobieski, she was one of Europe's wealthiest heiresses. Princess Maria Klementyna was betrothed to Prince James Stuart. King George I of England was opposed to the marriage because he feared that there would be an heir and, in order to placate him, the Austrian Emperor, Charles VI arrested Princess Maria Klementyna while on her way to Italy to marry James Stuart. She was confined in Innsbruck Castle but eventually the guards were deceived and Maria Klementyna escaped to Bologna, Italy, where, just to be safe from further intrusions, she was married by proxy to James who was in Spain at that time. Maria Klementyna's father, Prince James Louis Sobieski, approved her escape declaring that, as she became engaged to Prince James she ought to "follow his fortune and his cause".

Maria Klementyna and James Stuart were formally married on September 3, 1719 at Montefiascone , Italy in the Cathedral of Santa Margherita. Following their marriage, James and Maria Klementyna were invited to reside in Rome at the special request of Pope Clement XI, who acknowledged them as the (Catholic) King and Queen of Britain. The Pope provided them with a papal guard of troops, gave them the Palazzo Muti in the Piazza dei Santi Apostoli in Rome to live in, plus a country villa at Albano. The Catholic Church also provided them with an annual allowance of 12,000 crowns out of the papal treasury.

Princess Maria Klementyna and James Stuart had two sons:

1. Charles Edward Louis Philip Casimir Stuart, (1720-1788), aka "Bonnie Prince Charlie"
2. Henry Benedict Stuart, (1725-1807)

James's married life proved turbulent and unhappy and soon after their second child’s birth, Maria Klementyna left him and went to live in Rome in the convent of St. Cecilia. It was more than two years before they reconciled. Clementina was proned to depression and anorexia. She acused her husband of adultery and he said it was sinful to leave him and her children. She spent most of her time praying.

Maria Klementyna died at the early age of 32 on January 18, 1735. She was interred with full royal honors in St. Peter's Basilica in Vatican City. Pope Benedict XIV commissioned Pietro Bracchi (1700-1773) to sculpt a monument to her memory to be erected in the Basilica.