The King of the Belgians, Albert II, has announced his abdication.
In a national televised address, the 79-year-old monarch said he would step down in favour of his son Crown Prince Philippe, 53, on 21 July, Belgium's national day.
He said his health was no longer good enough to fulfil his duties, and he would step down after nearly 20 years on the throne.
King Albert was sworn in as the sixth king of the Belgians on 9 August 1993.
His accession to the throne followed the death of his brother, King Baudouin, at the age of 62.
"I realise that my age and my health are no longer allowing me to carry out my duties as I would like to," he said in his address.
"Prince Philippe is well prepared to succeed me."
King Albert met the Belgian government's cabinet earlier on Wednesday to inform them of his decision, Belgian state TV reported.
After he succeeded his brother, King Albert became embroiled in a major royal scandal when he was alleged to be the father of an out-of-wedlock daughter, Delphine Boel, and suffered a crisis in his marriage with Queen Paola.
That issue came to the fore again this spring when Ms Boel opened court proceedings to prove she was the king's daughter. There is some speculation in the media that this may have influenced his decision to abdicate.
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.
King Albert exercised his authority in mediating between political leaders on the formation of a government during the 2010-2011 parliamentary stalemate, when Belgium was left without a government for 541 days after elections failed to find a clear winner.
Tensions between the two main language communities of Flemish and French sometimes run high, and the issue has brought down several governments, creating frequent political instability.
Respect for the royal family, though, is one of the few factors that crosses the communal divide.
King Albert's announcement comes only three months after Queen Beatrix of the neighbouring Netherlands vacated the Dutch throne in favour of her son Willem-Alexander.