Should Leonor ascend to the throne as expected, she will be Spain's first queen regnant since her fourth great-grandmother Isabella II,[c] who reigned from 1833 to 1868.

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.

[8] Like her father, Leonor was baptized – with water from the Jordan River – in a Romanesque baptismal font that has been used to christen Spanish princes since the 17th century.

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.

[16] In September 2021, Leonor began studying a 2-year International Baccalaureate program at the UWC Atlantic College in the Llantwit Major, Wales.

[19] She is fluent in Spanish, Catalan and English (the latter learnt from her British nanny and also from her grandmother, Queen Sofía)[20] and has studied French, Galician, Basque, Arabic and Mandarin.

[23] In this sense, in March 2023, the minister of defense, Margarita Robles, announced that the government had approved a royal decree for Leonor to begin a 3-year military training education program.

[33] In June 2024, she closed the maneuver practices of the army training in the mountains of Navaleno and San Leonardo de Yagüe in Soria province.

[35] Leonor was promoted to the rank of Cadet Ensign (Spanish: Alférez) and awarded the Grand Cross of Military Merit by her father King Felipe VI on 3 July 2024.

[36] On 23 July 2024, the Council of Ministers appointed her as Midshipman (Spanish: Guardiamarina), preliminary step to join the Naval Military School at the end of August.

Under the current law, however, if her father has a legitimate son while still king, Leonor would be displaced in the line of succession and again become an infanta of Spain.

[15] There have been discussions[49][50][51] about changing the succession law to absolute primogeniture, allowing for the inheritance of the eldest child, regardless of sex; however, the birth of Leonor, followed by that of her younger sister Sofía, stalled these plans.

[57] In September 2018, Leonor conducted her first public engagement outside the palace by accompanying her parents to Covadonga to celebrate the 1,300th anniversary of the Kingdom of Asturias.

[58] On 31 October 2018, Leonor gave her first public speech, held at the Instituto Cervantes in Madrid, where she read the first article of the Constitution of Spain.

[61] She made her first speech on 4 November 2019 at the Princess of Girona Foundation awards in Barcelona,[62] in which she spoke in Spanish, Catalan, English and Arabic.

[63] Leonor carried out her first public solo engagement on 24 March 2021 by attending a ceremony to mark the 30th anniversary of the Instituto Cervantes.

[85] Since then, Leonor is generally styled as "Her Royal Highness The Princess of Asturias", although depending on the province of the country, another title may be added.

[88][89] Also, as traditional for the first in line to the throne, her father invested her with the insignia (Collar, Medal and Bow) of the Order of the Golden Fleece (awarded 30 October 2015, presented 30 January 2018).

[94][95] On 12 July 2024, she was awarded by the President of the Portuguese Republic, Marcelo Rebelo de Sousa, the Grand Cross of the Military Order of Christ.