Regent of Savoy
Declared Regent of her eleven-year-old son's dominions, she took her new charge with great interest and ambition. She carried on her husband's work on the properties of Savoy, supporting construction projects, artistic organizations, and educational institutions. She supported the work of Alessandro Stradella, protecting him when he fled to Turin from Venice. She continued to fund and support the work of Guarino Guarini, who completed the chapel for the Shroud of Turin and a Jesuit college under her rule. She also worked to expand the city of Turin down to the Po river. She attempted to start a university in Chambéry, but was not successful.
She did much to maintain links with her powerful neighbour France, which was both ally and family. She was criticised for wanting to maintain power too much, and for being a puppet of Louis XIV. However, she also worked to maintain and develop relationships with the royal courts of Spain, England, and the Empire. The people of Mondovì resisted her authority for many years, and it was only under her son that they finally relented.
Her relationship with her only son was always strained. This tension has been blamed on her ambition to keep power to herself. Marie Jeanne Baptiste spent most of her time working on state business, which she enjoyed, and had little time for her only child. She kept him under close scrutiny in order to make sure he would not try to assume power from her. Despite the bad relationship with her son, she openly kept lovers at court. At the age of thirty three, she was in a relationship with the Count of Saint Maurice, some ten years her junior. Marie Jeanne Baptiste and Saint Maurice's relationship lasted some four years before his whole family left in disgrace due to his father failing on a string of diplomatic relations.
By 1677 Marie Jeanne Baptiste was looking to organise a marriage for her son who would reach his majority in May 1680. Popular candidates were the Archduchess Maria Antonia, a cousin in Portugal, Maria Sofia of the Palatinate-Neuburg, or the French born Anne Marie d'Orléans. Marie Jeanne Baptiste first looked to her sister in Lisbon whose only daughter the Infanta Isabel Luísa was the heiress to her father's dominions. Portuguese law stated that an heiress to the throne must remain in the country and marry a kinsman. Marie Jeanne Baptiste opened negotiations with Portugal in order to get the Infanta to marry her son. This prestigious union would have left Marie Jeanne Baptiste permanently in control of Savoy, with Victor Amadeus II living in Portugal. Plans were made for Victor Amadeus' arrival in Lisbon, and a political party was established opposing the union. Openly disliking the union and approaching his majority, Victor Amadeus II decided to postpone the marriage for two years.
Marie Jeanne Baptiste then looked to the Grand Duchy of Tuscany which offered Anna Maria Luisa de' Medici as a bride. Negotiations were kept secret from France. This match was popular as it would give a powerful ally in Italy and was even favoured by Victor Amadeus II. The secret correspondence between Savoy and Tuscany has since been lost and the match never materialised.
Even though Marie Jeanne Baptiste's regency officially ended in 1680 she did not hand over power until 1684 when forced to do so by her son. Louis XIV was eager to maintain his already considerable influence in Savoy and thus offered his niece Anne Marie d'Orléans. Anne Marie was the daughter of Philippe of France, Duke of Orléans and his first wife Henrietta of England. Victor Amadeus agreed to the match and he married Anne Marie in person on 6 May 1684.
