Mariana of Austria (1634-1696) ruled the Spanish global empire during the minority of her son, Carlos II from 1665 to 1676. Her late husband’s will, combined with longstanding dynastic and Iberian legal, political, and socio-cultural traditions gave Mariana tremendous authority. Her unified regency — she had both executive authority over the government and guardianship power over the king — meant she had the power necessary to steer the monarchy during one of its most difficult junctures.

Spain’s war against Portugal’s bid for independence was essentially lost; decades of enormous military commitments had left Mariana saddled with a virtually bankrupt state, vulnerable frontiers, and a substantially reduced army. Spain’s traditional enemy, the Bourbons of France, was poised to attack. Compounding these challenges was the looming threat of a dynastic crisis. Carlos II was king, but he was three-years-old in an era in which children often died young. Meanwhile, his two older sisters, one married to the French king, the other promised to the Holy Roman Emperor, had succession rights. The Spanish empire’s global reach meant the regency had enormously high stakes: if Carlos died, the contested succession would likely bring a continent - wide war and perhaps a dismemberment of the Spanish monarchy.

During her decade-long regency, Mariana led the monarchy out of danger and helped redefine the military and diplomatic blocs of Europe. She made peace with Portugal, strengthened Spain’s defenses, and rebuilt the Spanish army. She broke Spain’s diplomatic isolation, forging leagues, coalitions, and agreements with England, the United Provinces, the Holy Roman Empire, and Sweden, Brandenburg, and Denmark. The monarchy she passed on to Carlos II was virtually intact and stronger than it had been at the beginning of her rule.

Despite her success as regent, she stumbled at a key transition: turning power to Carlos II when he turned fourteen. On the very day of Carlos emancipation, a failed coup tried to separate Mariana from her son, and fourteen months later, she was exiled from court. Carlos put power into the hands of Mariana’s enemy, Don Juan of Austria (1629-1679), the late king’s illegitimate son. Over the next two-and-a-half years, Mariana used her extensive connections and diplomatic experience to move the negotiations for her son’s marriage forward, effectively using the process to regain her position. She returned to Madrid triumphantly on September 1679, where she remained until her death of breast cancer on May 1696.

To reconstruct Mariana’s regency, exile, and subsequent return to court, this study uses multiple -archives to create a rich documentary foundation that includes Council of State deliberations, diplomatic correspondence and instructions, letters of Mariana and Carlos, manuscripts, royal-household papers, and legal documents. In Mitchell’s revisionist account, not only does Mariana emerge as a towering figure at court and on the international stage, but those around her — not just Carlos, but the key collaborators, the secretaries, ministers, and diplomats who have usually been ignored or undervalued — take their rightful place in history.