To honour the Spanish royal's birthday, HELLO! Online has gathered a list of ten facts about the young princess.
1. Leonor was on 31 October 2005 at the Ruber International Clinic in Madrid, becoming the first child of the then Prince Felipe and Princess Letizia.
2. Three months later in January 2006, Leonor's baptism took place at Zarzuela Palace conducted by the Cardinal Archbishop of Madrid, Antonio Rouco Varela. Her godparents were her paternal grandparents, King Juan Carlos and Queen Sofia.
3. In 2007, Leonor became a big sister when her parents Felipe and Letizia welcomed their second child, Infanta Sofia.
4. In September 2008, the young princess started her first year at the Santa Maria de los Rosales elementary school in Aravaca, outside Madrid.
5. On 14 June 2014, her grandfather King Juan Carlos abdicated in favour of his son Felipe, meaning at eight years old Leonor became the youngest heir presumptive in Europe and the future queen of Spain.
6. From her birth, the young royal held the title "Her Royal Highness Infanta Leonor of Spain," however after her father's accession to the throne, she became "Her Royal Highness The Princess of Asturias".
Princess Leonor (right) with her younger sister Infanta Sofia and mum Queen Letizia
7. She also holds the titles Princess of Girona, Princess of Viana, Duchess of Montblanc, Countess of Cervera and Lady of Balaguer.
8. Despite only being nine years old, the princess has supported her parents on a few engagements, most recently at Spain's National Day, which took place on 12 October.
9. When Leonor ascends the throne, as expected, she will be Spain's first queen regent since Isabella II, who reigned from 1833 to 1868.
10. The royal shares her birthday with child star Willow Smith and former The O.C. actress Samaire Armstrong.