Princess Leonor of Spain has come of age. Queen Letizia and King Felipe’s eldest daughter celebrated her milestone 18th birthday on Tuesday, Oct. 31.

The Princess of Asturias followed in her father’s footsteps, swearing an oath to the Spanish constitution in front of the Cortes Generales. “I swear to faithfully carry out my duties, to uphold and ensure that the Constitution and the laws are upheld, to respect the rights of citizens and the Autonomous Communities, as well as loyalty to the King,” Leonor said, while her parents and younger sister Infanta Sofia proudly watched.

Following the swearing-in of the constitution, Leonor was presented with medals and signed the Book of Honor of the Congress of Deputies. The royal family later moved to the Royal Palace of Madrid, where King Felipe bestowed the Collar de la Real y Distinguida Orden Española de Carlos III (The Royal and Distinguished Spanish Order of Charles III) upon his firstborn. His Majesty received the civil order—which was established by King Carlos III in 1771—back in 1986.

“Upon turning 18 today, and reaching the age of majority, I have taken the oath provided for in our Constitution. I have sworn to faithfully carry out my duties, to uphold and ensure that the Constitution and the laws are upheld, to respect the rights of citizens and the autonomous communities, as well as loyalty to the King,” Leonor said in her remarks at the ceremony (translated to English).

The Princess also declared, “I owe myself from today to all Spaniards, whom I will serve at all times with respect and loyalty. There is no greater pride. On this important day - which I will always remember with emotion - I ask you to trust me, as I have placed all my trust in our future, in the future of Spain.”

The heir to the Spanish throne was dressed in a white pantsuit with her hair swept up in a low ponytail for her big day. According to HOLA! Spain, the King and Queen will be hosting a private celebration for family at El Pardo palace on Tuesday.