Crown Prince Philippe has ascended to the Belgian throne amid fanfare and festivity after his father Albert 11's abdication, and he's vowed to prevent the breakup of a nation split by language and history.
The new monarch, who at 53 becomes "King of The Belgians", was sworn into office by the joint houses of parliament shortly after Albert, aged 79, stepped down citing age and failing health.
"I swear to abide by the constitution and laws of the Belgian people, to maintain national independence and the integrity of the land," Philippe, dressed in full military uniform, said in the country's three languages - French, Flemish and German.
President Barack Obama sent his best wishes to both the old and the new kings of a longtime ally that hosts key global institutions, the EU and NATO.
With political tension on the rise between the country's two main regions - Dutch-speaking northern Flanders and the French-speaking south - the monarch is a unifying force in the country of 11.5 million at the heart of Europe.
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"I begin my reign with the will to serve all Belgians," Philippe said to a standing ovation in his first speech as king.
"Belgium's strength lies in giving meaning to our diversity," King Philippe added as cannons boomed out a 101-gun royal salute.
But the head of the country's powerful northern separatist movement, the N-VA, snubbed the swearing-in and supporters refused to applaud.
Under sunny skies and a light breeze, flags fluttered across Brussels, which threw a mega-party for the new ruling couple that brought half a million people into the streets.
Flanked by his popular wife Mathilde, Belgium's first native queen, Philippe and their four young children faced a chorus of "Long Live the King" from 10,000 well-wishers when they turned out on the palace balcony.
"In another country I'd be a republican but here our kings play their role to perfection," said Olivier Leleux, a 40-year-old finance expert.
Belgium has fretted since Albert announced he was abdicating that the shy and often awkward Philippe, a trained fighter pilot who studied at Oxford and Stanford, might lack the political skills of his father to maintain unity in the divided nation.
