Luxembourg’s new Grand Duke

Luxembourg has a new monarch on the throne, and we are taking a look at the new Grand Duke Guillaume on the first day of his reign.

Guillaume Jean Joseph Marie was born on 11 November 1981 and became the heir to the throne, Hereditary Grand Duke, upon his grandfather’s abdication in 2000. He is half Luxembourgish and half Cuban.

His Royal Highness has four younger siblings, Prince Felix, Prince Louis, Princess Alexandra and Prince Sebastien.

The Grand Duke in 2009 with his parents. By Disquatufais – Own work, CC BY-SA 3.0, Wikimedia Commons

The Grand Duke was educated in England, France, Luxembourg, Switzerland and undertook military training at the UK’s Sandhurst. He also undertook internships at the Belgian Chemical Union, the Deutsche Bank, and the Spanish branch of ArcelorMittal.

In 2012, his engagement was announced to Belgian Countess Stéphanie de Lannoy. The pair married in October 2012 at Notre Dame Cathedral in Luxembourg City.

Grand Duke Guillaume and Grand Duchess Stéphanie have two sons, Hereditary Grand Duke Charles (the youngest heir in the world) and Prince François.

Maison du Grand-Duc / Sophie Margue

In his role as heir to the throne, Guillaume represented his father on the international stage and supported sports, music, and the youth. He also served as the patron to the Special Olympics Luxembourg Associations and was a member of the Luxembourg Scouts.

He was sworn in as the new Grand Duke of Luxembourg on 3 October 2025 after serving almost a year as the country’s regent. He is said to have the gentle nature of his father, and people are looking with curious eyes at the small European nation to see how he defines his reign.