Philippe takes over as Belgium's seventh sovereign facing the challenge of maintaining the unity of the linguistically-divided nation.
During 20 years on the throne, his father king Albert II's main task was to bridge the growing gap between Belgium's French-speaking south and Flemish-speaking north.
Criticised in some quarters as being too shy and diffident, Philippe said on taking the oath as king that he would rise to the same challenge.
"I begin my reign with the will to put myself at the service of all Belgians," Philippe told parliament.
Speaking in the country's three official languages -- French, Flemish and German -- he pledged to respect the constitution and maintain Belgium's "independence and territorial integrity".
"Some parties ... want to rip our country up. They'll have me to deal with -- I can be fearsome, I won't take anything lying down," he had said more bluntly in 2004.
Born in Brussels on April 15, 1960, the 53-year-old is the eldest son of Albert II who came to the throne on the death in 1993 of his brother king Baudouin, who had no children.
In 1999, Philippe married Mathilde d'Udekem d'Acoz, a charming Belgian aristocrat 13 years his junior, who brought a touch of glamour to the otherwise staid Belgian monarchy.
Philippe and the popular Mathilde have four children, including Princess Elisabeth who was born in 2001 and who is in line to be Belgium's first female head of state after the Salic succession law was changed to end the automatic right of the eldest male heir to take the throne.
Philippe has two siblings -- Astrid who is married to Archduke Lorenz of Austria-Este and Laurent, the "enfant terrible" of the Belgian royal family.
But he may also have a half-sister, Delphine, an artist who insists she is Albert's illegitimate daughter.
In the 1960s and 1970s, when relations between Albert -- then crown prince -- and Paola were at their worst, the couple paid little attention to their children, more often than not leaving them in the hands of friends or with staff among the royal household.
As a youngster Philippe was timid and had a Roman Catholic education in Brussels and in Flanders without ever shining particularly.
He went on to military school, training as a fighter pilot and paratrooper before going to Oxford and Stanford but as a young man remained introverted and apparently ill at ease in public.
In 1993 when his mentor king Baudouin died, some had expected that the then 33-year-old would succeed but it was felt Philippe was "not ready" and instead Albert stepped onto the throne.
In the years since, Philippe has gained in assurance and headed dozens of economic missions for Belgium across the globe.
"You have all the qualities to serve your country well," Albert said Sunday of his son. "You and your dear wife Mathilde have all our confidence."
© 2013 AFP
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