Crown Princess Elisabeth of Belgium returned from a Welsh boarding school for her lavish 18th birthday party.
When she eventually ascends the throne, she will be the first-ever Queen of Belgium by birth.
The princess travelled to Brussels for the official birthday ceremony from her boarding school UWC Atlantic College in south Wales.
Her birthday now means she is officially old enough to rule without a regent being appointed.
Before the heir to the throne delivered a speech to a room full of guests at the Royal Palace, her father presented her with the Order of Leopold, the order order of chivalry or knighthood in Beligum.
Princess Elisabeth said: "Eighteen years is the transition to adulthood ... The country can count on my commitment."
King Philippe also gave a speech at the event, before guests enjoyed performances by the Royal Ballet School of Antwerp and Eurovision singer Blanche.
Addressing the audience he said: "Happy birthday, my dear Elisabeth. Spread your wings, be happy. This is what I wish you wholeheartedly."
The ceremony was broadcast live across three Belgium TV channels, giving Belgian's the opportunity to celebrate with the royal family on the historic day.
Typically, the broadcasting of royal events in Belgium is reserved for weddings and funerals.
