Philippe has been sworn in as the sixth King of the Belgians, following the abdication of his father King Albert II after 20 years on the throne.
Philippe, 53, is stepping into a role that is largely ceremonial.
The Belgian monarch can be a key mediator in a country that is split down the middle, into Dutch-speaking Flanders and French-speaking Wallonia.
Upon being sworn in, King Philippe spoke of cohesion: “I start my reign with a willingness to put myself at the service of all Belgians. To do this I will work in harmony with the government, in accordance with the constitution.”
Earlier, Albert II signed an official abdication act during an emotional ceremony.
Albert said his final recommendation was that the royals and the government should work without rest to keep Belgium together.