Isabella Clara of Austria (12 August 1629 – 24 February 1685) was a Duchess consort of Mantua, Montferrat, Nevers (until 1659), Mayenne (until 1654) and Rethel (until 1659) by marriage to Charles II, Duke of Mantua and Montferrat.
From 1665 to 1671, she was Regent of the Duchies of Mantua and Montferrat on behalf of her minor son. Accused of marrying her lover without Imperial consent, she was forced to take the veil as a nun and imprisoned at the Ursuline monastery of Mantua until her death.
Life
Birth and family
Isabella Clara was born in Innsbruck on 12 August 1629 as the third child and second (but eldest surviving) daughter of Leopold V, Archduke of Further Austria and Count of Tyrol and his wife Claudia de' Medici. Her grandparents on her father's side were Charles II, Archduke of Inner Austria and his wife Princess Maria Anna of Bavaria. Her grandparents on her mother's side were Ferdinando I de' Medici, Grand Duke of Tuscany and his wife Princess Christina of Lorraine.
From her mother's first marriage, she had an older half-sister, Vittoria della Rovere, Duchess of Rovere and Montefeltro suo jure and later Grand Duchess consort of Tuscany. Of her four surviving full siblings, her sister Maria Leopoldine was briefly Holy Roman Empress, German Queen, Queen consort of Hungary and Bohemia until her death in childbirth in 1649. Her two brothers Ferdinand Charles and Sigismund Francis were the last male members of their branch who ruled Further Austria and the County of Tyrol.
Duchess of Mantua
On 7 August 1649, the marriage contract between Isabella Clara and Charles II Gonzaga, Duke of Mantua and heir of the Duchy of Montferrat, was signed at Innsbruck. Considering the size of the bride's dowry, the contract stipulated that all the revenues of the Gazzuolo district must be given to her. The official wedding between them was solemnized three months later, on 7 November in Mantua. Thanks to this alliance with the House of Habsburg, Charles II was able to remove the French from Casale and then agreed with King Louis XIV of France that Spain should not control the Duchy of Montferrat; rather, it would remain with the Gonzaga family.
Charles' mother Maria Gonzaga, Duchess of Montferrat and former Regent of the Duchy of Mantua –who was an adherent to follow a pro-Austrian foreign policy– and her paternal aunt Eleonora Gonzaga, Dowager Holy Roman Empress organized the union. In March 1651, together with her husband and mother-in-law, Isabella Clara accompanied her sister-in-law, Eleonora Gonzaga, for her wedding with Ferdinand III, Holy Roman Emperor in Wiener Neustadt. They remained in the Imperial court until May, when they returned to Mantua.
In Revere on 31 August 1652, Isabella Clara gave birth to her only child, Ferdinand Charles, the future and last Duke of Mantua and Montferrat of the House of Gonzaga; however, this didn't help the couple overcome their differences. Charles II was indifferent to his wife –whom he married purely for political reasons–, and had a long-standing relationship with the Countess Margherita della Rovere, also living at Casale with della Rovere openly. Isabella Clara, with the help of Pope Alexander VII, expelled her husband's mistress to Rome; but this didn't stop the hypersexuality of Charles II, who continued taking lovers, both male and female.
Isabella Clara soon tired of her husband's behaviors and, in spite of her mother-in-law's requests that she be prudent, Isabella Clara also took a lover, Count Charles Bulgarini, a secretary of the Duke and a baptized Jew from the Mantua ghetto. They had a secret relationship initially, but the affair became well-known in time. Consequently, Isabella Clara suffered the rejection of and contempt from the Ducal court. In June 1661, an assassination attempt was made against the Count Bulgarini, but the shot killed his father. In 1660, after the death of her mother-in-law, Isabella Clara also took the title of Duchess of Montferrat. When Charles II died suddenly on 14 August 1665, there were rumors that his wife ordered that he would be poisoned. In fact, the Duke died either accidentally after drinking an aphrodisiac, or in the midst of lascivious intercourse.
Regency
During her husband's life, Isabella Clara relied on the advice of her lover and controlled the political situation in the Duchy. When she became a Regent on behalf of her minor son, she appointed Count Bulgarini as her First Minister and took a neutral position between the Spanish and French Kingdoms and also kept a cautious policy to ensure that Mantua and Montferrat would become independent from the Holy Roman Empire.