The question of Maria Theresa’s marriage arose early in her childhood. Initially, Leopold Clement of Lorraine was considered a suitable match, and plans were made for him to visit Vienna and meet the young archduchess in 1723. However, these plans were derailed by his untimely death from smallpox that same year.
Following Leopold Clement’s death, his younger brother, Francis Stephen, was invited to Vienna. Although Emperor Charles VI favored Francis Stephen as a potential husband for Maria Theresa, he explored other alliances as well. Religious differences ruled out a match with the Protestant prince Frederick of Prussia. In 1725, Charles VI arranged a double engagement: Maria Theresa was betrothed to Charles of Spain, while her sister, Maria Anna, was promised to Philip of Spain. However, political pressures from other European powers forced him to abandon this arrangement, and the engagement with Charles was annulled. This decision pleased Maria Theresa, who had grown close to Francis Stephen.
Francis Stephen remained at the imperial court until 1729, when he inherited the Duchy of Lorraine. Despite their growing bond, Maria Theresa was not formally betrothed to him until 31 January 1736, during the War of the Polish Succession. The engagement came at a cost: France’s King Louis XV demanded that Francis Stephen cede Lorraine to his father-in-law, Stanisław I, the deposed king of Poland. In exchange, Francis Stephen was promised the Grand Duchy of Tuscany upon the death of its childless ruler, Gian Gastone de’ Medici.
Maria Theresa and Francis Stephen were married on 12 February 1736 at the Augustinian Church in Vienna.
Maria Theresa was deeply devoted to her husband, expressing her affection in letters filled with longing and excitement before their marriage. In contrast, Francis Stephen’s responses were more reserved and formal. Their marriage faced challenges, particularly Maria Theresa’s jealousy and Francis Stephen’s infidelities, including his well-known affair with Maria Wilhelmina, Princess of Auersperg.
When Gian Gastone died on 9 July 1737, Francis Stephen relinquished Lorraine and assumed the title of Grand Duke of Tuscany. The couple made a ceremonial entry into Florence, where a Triumphal Arch was constructed in their honor at the Porta Galla, a structure that stands to this day. Their stay in Tuscany was brief, as Charles VI recalled them to Vienna, fearing his death might leave his heiress far from the imperial court. During the summer of 1738, Austria suffered significant losses in the Russo-Turkish War, leading to public unrest in Vienna. Francis Stephen faced criticism and suspicion, being accused of cowardice and labeled a French spy. The conflict concluded with the Treaty of Belgrade in 1739.