Emmanuel Philibert, Duke of Savoy
Shortly before her 36th birthday, a marriage was finally arranged for her by her brother King Henry II of France and her former suitor Philip II as part of the terms stipulated in the Treaty of Cateau-Cambrésis which was signed by the ambassadors representing the two monarchs on 3 April 1559. The husband selected for her was Philip's ally, Emmanuel Philibert, Duke of Savoy, Prince of Piedmont. At the time, Margaret was described as having been a "spinster lady of excellent breeding and lively intellect".