Grand Duke Guillaume; Credit: Ali Sahib, Chronicle.lu

Just over a year after ascending the throne, Grand Duke Guillaume of Luxembourg is celebrating his 45th birthday, tomorrow, on Wednesday 11 November 2026.

Born Guillaume Jean Joseph Marie on 11 November 1981 at the Grand Duchess Charlotte Maternity Hospital, he is the eldest son of Grand Duke Henri and Grand Duchess Maria Teresa. He married Countess Stéphanie de Lannoy (now Grand Duchess Stéphanie) at Notre-Dame Cathedral on 20 October 2012, and the couple have two sons: Prince Charles (born 10 May 2020), who is now first in line to the throne, and Prince François (born 27 March 2023), second in line.

After serving as “Lieutenant-Représentant” (Lieutenant-Representative) from 8 October 2024, when he became the first Hereditary Grand Duke to take the oath before the full Chamber of Deputies, Guillaume ascended the throne on 3 October 2025, marking the end of the 25-year reign of his father.

Since his accession to the throne, Grand Duke Guillaume has held numerous meetings with the public and representatives of Luxembourg society, while continuing to represent the Grand Duchy internationally.

Over the years, he has supported numerous causes in Luxembourg, paying particular attention to social cohesion, vulnerable people and young people. He has also been involved in promoting Luxembourg's economy and strengthening its international relations.

Grand Duke Guillaume began his education at the primary school in Lorentzweiler and continued his secondary studies at Lycée Robert Schuman in Luxembourg City. At the age of sixteen, he attended Institut Le Rosey and later the Collège Alpin Beau Soleil in Switzerland, where he obtained his French Baccalaureate in 2001. He is fluent in Luxembourgish, French, German, English and Spanish.

Following his officer training at the Royal Military Academy Sandhurst (RMAS) in the United Kingdom, he was sworn in as an officer of the Luxembourg Army in December 2002. He later held the rank of Colonel before becoming Commander of the Luxembourg Army upon his accession to the throne.

He studied international politics in the UK and earned a double degree in Arts and Political Science with honours from the University of Angers in France in 2009. He also gained experience through internships at Union Chimique Belge and Deutsche Bank in London in 2003 and 2004, as well as training at ArcelorMittal in Spain in 2005.

From 2018 to 2019, the Grand Duke completed a postgraduate course at the Royal College of Defence Studies (RCDS) in London, further preparing for his future responsibilities as Head of State. In 2018, the Miami University John E. Dolibois European Center (MUDEC) in Luxembourg awarded him its highest honorary distinction, Doctor honoris causa (Honorary Doctorate), for his public and social engagement.