Princess Leonor, Spain Future Queen has sworn an oath to the constitution at a formal ceremony on her 18th birthday in Madrid.
The first in line to the throne, Leonor received a standing ovation after reciting the oath during a joint session of the Spanish Congress and Senate.
The ceremony in parliament marked her coming of age, meaning she will now directly become queen after her father King Felipe VI, assuming he does not go on to have any male children.
The princess, who went to school in Wales and started three years of military training in Spain in August, vowed to uphold the law, respect the rights of citizens and regions and be faithful to the king.
Most cabinet ministers and regional leaders looked on as she paraded into parliament and took her oath in a music-filled blaze of pageantry broadcast live on television.