Princess Maria Christina of the Two Sicilies (Italian: Maria Cristina Ferdinanda di Borbone, principessa delle Due Sicilie, Spanish: María Cristina de Borbón, princesa de las Dos Sicilias; 27 April 1806 – 22 August 1878) was Queen consort of Spain (1829 to 1833) and Regent of Spain (1833 to 1840).

Born in Palermo, Sicily on 27 April 1806, she was the daughter of King Francis I of the Two Sicilies by his second wife, Maria Isabella of Spain.

With the death on 27 May 1829 of the third wife of Ferdinand VII of Spain, the Spanish king was in need for a male heir to succeed to the crown. This led to his fourth marriage, just seven months later (11 December 1829), to Maria Christina. If the rushed marriage was not awkward enough, King Ferdinand was also her uncle by both birth and marriage. Maria Christina's mother, Maria Isabella, was King Ferdinand's sister; both were born to King Charles IV of Spain and his wife, Maria Luisa of Parma.

As queen, Maria Christina, rapidly delivered two daughters, the future Queen Isabella II (1830–1904), and the Infanta Luísa Fernanda (1832–1897), and two sons who did not survive past one year.

When Ferdinand died on 29 September 1833, Maria Christina became regent for their daughter Isabella. Isabella's claim to the throne was disputed by her uncle, the Infante Carlos, Count of Molina, who claimed that his brother Ferdinand had unlawfully changed the succession law to permit females to inherit the crown (see Carlism). Some supporters of Don Carlos went so far as to claim that Ferdinand had actually bequeathed the crown to his brother but that Maria Christina had suppressed that fact. It was further alleged that the Queen had signed her dead husband's name to a decree recognizing Isabella as heir.

...
Wikipedia