Holy Roman Emperor and Grand Duke of Tuscany, though his wife effectively executed the real powers of those positions. With his wife, Maria Theresa, he was the founder of the Habsburg-Lorraine dynasty. From 1728 until 1737 he was Duke of Lorraine. In 1737, Lorraine became managed by France under terms resulting from the War of the Polish Succession. Francis and the House of Lorraine received the Grand Duchy of Tuscany in the peace treaty that ended that war. After taking the throne of the Holy Roman Empire, the return of the ancestral duchy of Lorraine went nominally to his brother Prince Charles Alexander of Lorraine (who was however engaged in ruling the Austrian Netherlands), until succession under derivate house alliances resulted in Lorraine’s annexation to France in 1766.
Maria Theresa and Francis I had sixteen children—their youngest daughter was the future queen consort of France, Marie Antoinette (1755–1793). He was officially succeeded by his eldest son Joseph II although the real power remained with his wife. Another son was the Emperor Leopold II.
Francis was quite the philanderer and was known for his many indiscreet affairs, notably one with Maria Wilhelmina, Princess of Auersperg, who was thirty years his junior. This particular affair was remarked upon in the letters and journals of visitors to the court and in those of his children.
He died suddenly in his carriage while returning from the opera at Innsbruck on 18 August 1765.
Link to Wikipedia biography