Leonor, Princess of Asturias (Leonor de Todos los Santos de Borbón y Ortiz; born 31 October 2005) is the heir presumptive to the Spanish throne. She is the elder daughter of King Felipe VI and Queen Letizia.

Leonor was born during the reign of her paternal grandfather, King Juan Carlos I. She was educated at Santa María de los Rosales School, like her father; after finishing her secondary studies, she studied for an International Baccalaureate at the UWC Atlantic College in the Vale of Glamorgan in Wales, United Kingdom. In 2014, following her father's accession to the throne after the abdication of her grandfather, Leonor was granted all the traditional titles of the heir to the Spanish crown. These are Princess of Asturias, Princess of Girona, Princess of Viana, Duchess of Montblanc, Countess of Cervera, and Lady of Balaguer. Leonor was formally proclaimed heiress before the Cortes on 31 October 2023, her 18th birthday.

Before pursuing higher education, Leonor completed three years of military training, graduating as an officer in all three branches of the Spanish Armed Forces.

Leonor was born on 31 October 2005 at 01:46, three weeks before her due date, to Felipe and Letizia, then the Prince and Princess of Asturias, during the reign of her paternal grandfather, King Juan Carlos I, in the Ruber International Hospital in Madrid using a caesarean section necessitated by non-progression of labour. As the daughter of the heir apparent, she was an infanta and the second in the line of succession to the Spanish throne. Her birth was announced by the royal family to the press via SMS.

Shortly after her birth, Leonor's umbilical cord stem cells were sent to a blood bank in Tucson, Arizona. This decision sparked public debate in Spain, as the blood bank was private and located abroad.

Leonor left the Ruber International Hospital with her parents on 7 November 2005. She was baptised in the Zarzuela Palace by the archbishop of Madrid, Cardinal Antonio Rouco Varela, on 14 January 2006. Like her father, Leonor was baptised – with water from the Jordan River – in a Romanesque baptismal font that has been used to christen Spanish princes since the 17th century. Her godparents were her paternal grandparents, King Juan Carlos I and Queen Sofía. She received the name of Leonor de Todos los Santos.

During her early months, Leonor developed a small angioma, a benign tumour of blood vessels, on her nose. The angioma, which was visible during her baptism, was initially mistaken for a scratch. According to medical sources, such angiomas are common in newborns and typically disappear within a year or year and a half without the need for surgery. Despite media speculation about potential surgery, sources close to the Royal Family confirmed that no such procedure was ever considered, and the angioma disappeared within months.

Leonor's education began in 2007 at Escuela Infantil Guardia Real, the daycare for the children of the Spanish Royal Guard. She began her first year of pre school on 15 September 2008 at the Santa María de los Rosales School in Aravaca, Madrid. She later began her first year of primary school in September 2011 at the Santa María de los Rosales School. Leonor was reported to have good grades during her studies in Rosales.