Crown Prince Philippe has been sworn in as the new king of Belgium after the abdication of his father Albert II. He took the oath as the country's seventh king in a ceremony in parliament.
To warm applause on Belgium's national day on Sunday, King Philippe, 53, promised to uphold the constitution.
Belgium has a constitutional monarchy in which the king plays a largely ceremonial role.
One of the duties the monarch does have is trying to resolve constitutional crises.
In his final address before signing a legislative act to step down, King Albert, 79, stressed his wish that Belgium - split between the Dutch-speaking north and the French south - remained united.
His resignation on the grounds of ill-health came after nearly 20 years on the throne and was timed to coincide with Belgium's national day.
In a ceremony topped off by trumpet fanfare and cannon-fire, King Philippe took his oath in three official languages - Dutch, French and German.
A BBC correspondent said this was a reminder of the delicate political task that awaits him: trying to mediate across a divide between Wallonia and Flanders, where support for independence has been rising fast.
Tensions between the Dutch-speaking and French communities sometimes run high, and the issue has brought down several governments.
Belgium was left without a government for 541 days during the 2010-2011 after elections failed to find a clear winner.
Respect for the royal family is one of the few factors that crosses the communal divide.
Queen Beatrix of the Netherlands vacated the Dutch throne in favour of her son Willem-Alexander three months ago.
