Francis I was the Duke of Lorraine and Bar, and later Grand Duke of Tuscany, who married Maria Theresa of Austria and became Holy Roman Emperor and Archduke of Austria. His wife effectively ruled Austria and the Holy Roman Empire. They were the founders of the Habsburg-Lorraine dynasty. The oldest surviving son of Leopold, Duke of Lorraine, Francis left the duchy for the deposed Polish king Stanisław Leszczyński in exchange for the Grand Duchy of Tuscany as one of the terms ending the War of the Polish Succession in 1738. The duchy and the ducal title to Lorraine and Bar passed to King Louis XV of France upon Leszczynski's death in 1766, though Francis and his successors retained the right to style themselves as dukes of Lorraine and Bar.