Belgium's King Albert II says he will abdicate on July 21 and leave the throne to his son, saying at 79 he felt too old to carry out his duties properly.
Albert II, who has three children, ascended to the throne in 1993 when his childless brother Baudouin died.
His 53-year-old heir, Philippe, studied at Trinity College, Oxford, and Stanford University, and has led trade delegations to countries such as the United States, China and Thailand. In 1999 Philippe married Princess Mathilde, a Belgian-born aristocrat, with whom he has four children. His 11-year-old daughter Elisabeth could become the country's first queen.
While the monarch has no executive powers and plays a largely ceremonial role, he is a rare uniting factor in the linguistically divided country which in recent years has seen more powers devolved to regional governments.
''I realise that my age and my health are no longer allowing me to carry out my duties as I would like to,'' the king said in a televised address.
Prime Minister Elio Di Rupo said of Philippe: ''He has already shown repeatedly how much he loves Belgium and the prince is willing to serve the country well. He can count on the support of the government.''
The abdication of Albert II comes after Queen Beatrix of the Netherlands vacated the Dutch throne in favour of her son Willem-Alexander in April.
Outside the palace in central Brussels, a small crowd of people waved flags. ''We are here to welcome Philippe,'' said student Jerome Nsanzi, 26. ''I think he will have more energy than his father to maintain unity.''
In 2010 and 2011, when parties on both sides of the linguistic divide were locked in a record-setting 541 days of coalition talks to form a federal government, it was up to the king to appoint the party leaders heading the negotiations.
Philippe may face this task during the next federal elections in 2014.
Albert II, a renowned bon viveur, was popular with both people and politicians for his easy going style.
The monarchy has faced criticism from politicians and the local media, however, especially when it emerged that Queen Fabiola, the widow of King Baudouin, had planned to pass on an estate in Spain by using a trust to avoid paying tax.
The reports caused the Belgian government to reform the system of state allowances and taxation for members of the royal family.
In 1999, Belgian media reported that Albert had fathered a fourth child, a daughter, in an extramarital affair in the 1960s. The palace never acknowledged this.
Philippe is seen by many as a more reserved character than his father. He told a Belgian astronaut in 1992 that he should address him simply by his first name. ''I think there is absolutely no protocol in space,'' he said.