Ranuccio II Farnese (17 September 1630 – 11 December 1694) was the sixth Duke of Parma and Piacenza from 1646 until his death nearly 50 years later and Duke of Castro from 1646 until 1649. Ranuccio was the eldest son of Odoardo Farnese, the fifth sovereign duke of Parma, and his Tuscan wife, Margherita de' Medici. After his father's sudden death, Ranuccio succeeded as duke. As he was a minor and had not yet reached his majority, he ruled the first two years of his reign under the regency of his uncle, Francesco Maria Farnese and his mother. Ranuccio belonged to the House of Farnese, whose duchy were founded by his patrilineal ancestor, Pope Paul III, formerly Alessandro Farnese. The Farnese Dukes had been ruling Parma and Piacenza since Pope Paul's illegitimate son Pier Luigi Farnese was given it as a possession. Ranuccio refused to repay the debts incurred by his father, despite the latter having a signed a peace treaty agreeing to do so. He also refused to recognise the new bishop of Castro, appointed by Urban's successor, Innocent X. In 1649, the new bishop, Cardinal Cristoforo Giarda, was murdered on his way to Castro. Innocent accused Ranuccio of the murder and in retaliation; forces loyal to the Pope besieged Castro, and then razed it to the ground. In August of that same year the Parmense troops had been crushed not far from Bologna, and Ranuccio remained with no means to gain back his fief, despite his attempts to buy it back with money. In 1672 he bought the principate of Bardi and Compiano from Gianandrea Doria Landi, giving the Duchy its final shape. In the last days of his reign, the Duchy suffered heavily from the presence of Imperial troops, who were fighting in the dispute between Victor Amadeus II of Savoy and France. Ranuccio II was married three times. On 29 April 1660, Ranuccio married firstly Marguerite Yolande of Savoy (b. 15 November 1635 – d. 29 April 1663), a daughter of Victor Amadeus I, Duke of Savoy and Christine Marie of France. They had two children. On 18 February 1664 Ranuccio married secondly Isabella d'Este of Modena (b. 3 October 1635 – d. 17 August 1666), a daughter of Francesco I d'Este and his cousin. They had three children. On 1 January 1668 he married Maria d'Este of Modena, (b. 8 December 1644 – d. 20 August 1684), his second wife's sister. They had nine children.

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