Carlos Hugo, Duke of Parma and Piacenza (8 April 1930 – 18 August 2010) was the head of the House of Bourbon-Parma from 1977 until his death. Carlos Hugo was the Carlist pretender to the throne of Spain and sought to change the political direction of the Carlist movement through the Carlist Party, of which he was the official head during the fatal Montejurra Incident. His marriage to Princess Irene of the Netherlands in 1964 caused a constitutional crisis in the Netherlands.

Carlos Hugo was the son of Xavier, Duke of Parma, and Madeleine de Bourbon-Busset and was baptized Hugues Marie Sixte Robert Louis Jean Georges Benoît Michel. He was a direct male descendant of Louis XIV. On 28 June 1963 he was officially renamed Charles Hugues, by judgment of the court of appeal of la Seine, France.

In 1977, his father died, and Carlos Hugo succeeded him claiming the thrones of Parma, Etruria and Spain. He was a French citizen, and from 1980, a naturalized Spanish citizen.

He studied in Paris and at the University of Oxford.

Carlism is a Spanish political movement founded in the 19th century which, since the second half of the 20th century, upholds the claim of Carlos Hugo's branch of the House of Bourbon to the Spanish throne.

In 1952, Carlos Hugo's father publicly laid claim to the Spanish throne as Javier I, but he was ignored by Spanish dictator Francisco Franco, who later chose Juan Carlos to be his successor instead. On 5 May 1957 Javier proclaimed Carlos Hugo Prince of Asturias and Duke of San Jaime. In February 1964 Carlos Hugo assumed the title Duke of Madrid.

After alienating many Carlists during the mid-1960s by his attempts to approach Franco (on whom a 1947 organic law had conferred the right to select a king to succeed himself as head of state) Carlos Hugo's increasingly leftist politics prompted the prince to embrace Titoist socialism. As Xavier's health declined so too did his appearances as the Carlists' leader: two of Carlos Hugo's sisters living in Spain, both academics, publicly supported their brother's political transition, while his mother and brother, Prince Sixte-Henri, continued to live with his father in France and to adhere to traditional Carlism.

Carlos Hugo assumed Carlist leadership in August 1975. During the Franco regime, the organization of Carlism has been known as the Traditionalist Communion. After Franco's death, also the Carlist movement was badly split, and unable to get wide public attention again. In May 1976, a year after Franco's death, two Carlist sympathizers were shot down by far-right terrorists during the annual Carlist convocation. Among the terrorists were Stefano Delle Chiaie and members of the Argentine Anticommunist Alliance (Triple A), with logistic support from Francoist elements inside Spanish intelligence agencies and the Civil Guard.^[1][2] This incident became known as the Montejurra massacre.^[3]

In the first democratic elections on 15 June 1977, only one Carlist senator was elected, journalist and writer Fidel Carazo from Soria, who ran as an independent candidate. In the parliamentary elections of 1979, Carlists integrated in the coalition Unión Nacional, that won a seat in Congress for Madrid; but the elected candidate was Blas Piñar, Francoist leader of Fuerza Nueva. Since then, Carlists have remained extra-parliamentary, obtaining only town council seats.

Carlos Hugo abandoned his Carlist claims in 1979 and became a naturalised Spanish citizen as Carlos-Hugo de Borbón-Parma y Borbón, by royal decree of King Juan Carlos. In 1980, he left the political arena, abandoning the new "Partido Carlista" which he had created. The party would later become a founding member of the United Left coalition.

In 2002 Carlos Hugo donated his House's archives to Spain's national historical archives. This decision was opposed by his brother Sixtus.

On 28 September 2003 at Arbonne in France, Carlos Hugo re-asserted his Carlist claim.^[4] He announced that he would use the title Count of Montemolin (conde de Montemolín) for himself, and that three of his children would have Carlist titles: Duke of Madrid (duque de Madrid) for his son Carlos, Duke of San Jaime (duque de San Jaime) for his son Jaime, and Duchess of Guernica (duquesa de Gernika) for his daughter Carolina.

Carlos Hugo's engagement to Princess Irene of the Netherlands, daughter of Queen Juliana of the Netherlands, caused a constitutional crisis in the Netherlands for several reasons. Irene lost her rights of succession to the Dutch throne because the government refused to enact a law permitting the marriage. Her mother could not go to Madrid to talk Irene out of the marriage and of her conversion to Catholicism because the government advised her against it. The issue that prevented the government from making a law permitting the marriage was Carlos's claim to the Spanish throne. The Dutch government saw international political difficulties arising from a possible heir to the Dutch throne holding a controversial claim to the throne of a foreign state.

Carlos Hugo and Irene were married on 29 April 1964, in the Borghese Chapel at the Basilica di Santa Maria Maggiore in Rome, by Cardinal Paolo Giobbe, the former Apostolic Nuncio to the Netherlands.^[5] No other members of the Dutch Royal Family were present; Irene's parents watched the ceremony on television.^[6] After the ceremony, Carlos Hugo and Irene had a private audience with Pope Paul VI. They spent their honeymoon in Las Palmas de Gran Canaria, after which they settled in Madrid.^[7]

Carlos Hugo and Irene divorced on 26 May 1981.^[8] They had four children:

In February 2008 it was revealed that Carlos Hugo was being treated for cancer. On 2 August 2010, he announced, via his official website, that his health was further deteriorating.^[9] He died on 18 August 2010 in Barcelona at the age of 80. Carlos Hugo's remains were taken from Barcelona to The Hague and laid in state for family members and close relatives in the Fagel Dome on the estate of the Noordeinde Palace (one of the four official palaces of the Dutch royal family). On 28 August, the body was transported to Parma in Italy and interred in the crypt of the Sanctuary of Santa Maria della Steccata.^[10][11]

Carlos-Hugo claimed the headship of the Constantinian Order of Saint George as hereditary heir to the House of Farnese's Duchy of Parma, the Farnese dukes having been recognised as grand masters of the order in 1699, although in 1706 the church of Rome confirmed the order's grand magistry to the Farnese's heirs (the House of Bourbon since 1731) in accordance with male primogeniture.

As a claimant to the throne of Spain, Carlos Hugo also claimed to be the Grand Master of the Spanish Order of the Golden Fleece At his funeral the chain of the Order of the Golden Fleece was put on his coffin,^[20] and the prince wore the insignia of the order during his marriage.^[21]