‘Shadow Queen’ Fostier Steps Down as Mathilde’s Chief of Staff
Machteld Fostier, the veteran diplomat who has served as Queen Mathilde of Belgium’s closest advisor and chief of staff for more than 25 years, is stepping down from her role as Secretary to the Queen effective 1 September 2026. The Royal Palace announced the change on Friday, 24 July, and named experienced diplomat Marleen Steenbrugghe as her successor.
The End of an Era
Fostier, 67, has been a constant presence at Queen Mathilde’s side since the then-Princess Mathilde entered the royal family upon her marriage to Prince Philippe in 1999. Known in both Dutch and French as the “shadow queen” (“schaduwkoningin” / “reine de l’ombre”) for her influential behind-the-scenes role, Fostier has shaped the Queen’s public engagements for over two decades.
According to Het Laatste Nieuws, Fostier was officially appointed as Secretary to the Queen in 2013 when Mathilde became Queen consort following King Philippe’s ascension to the throne. Prior to that, she served as an advisor to the then-Princess Mathilde from 2008, with only a brief interruption between 2006 and 2008 when she headed the Belgian mission in Washington, D.C.
A Career of Quiet Influence
As Secretary to the Queen, Fostier held the highest-ranking position in the Queen’s office. Her responsibilities included daily consultations with the Queen, organizing audiences and meetings, preparing speeches, coordinating domestic and international visits, and providing substantive policy advice. The official monarchy website lists her title as “Secretaris van Hare Majesteit de Koningin: Ambassadeur Machteld Fostier.”
Her nickname “shadow queen” reflects her constant yet discreet presence. While she generally stayed out of the spotlight, Fostier was invariably seen at Mathilde’s side during work visits, foreign trips, and international meetings. Her 25-year tenure spans Mathilde’s entire journey from princess to queen, making her one of the most enduring figures in the Queen’s inner circle.
A Phased Transition
Despite stepping down as Secretary, Fostier will not disappear entirely from the Queen’s entourage. The Royal Palace has confirmed that she will continue to advise Mathilde in specific domains, though the exact areas have not yet been disclosed. This phased handover suggests a desire for continuity and stability within the royal household.
As RTL Info reported, “Le Palais souligne qu’elle continuera d’épauler Mathilde en tant que conseillère dans plusieurs domaines spécifiques” (The Palace emphasizes that she will continue to support Mathilde as an advisor in several specific domains).
Meet the Successor: Marleen Steenbrugghe
Fostier’s successor, Marleen Steenbrugghe, brings a strong diplomatic pedigree to the role. Currently serving as an advisor for multilateral affairs in the cabinet of Foreign Minister Maxime Prévot (Les Engagés), Steenbrugghe began her diplomatic career in 2009.
Her postings include the Permanent Representation of Belgium to the European Union (2010–2011), the Belgian Embassy in Bangkok (2011–2015), and extensive experience in Geneva. Between 2015 and 2020, she worked at the Belgian Representation to the United Nations, followed by five years at the Delegation of the European Union in Geneva (2020–2025). She holds a law degree and a Master’s in International Relations and Conflict Management.
Broader Context
Fostier’s departure comes amid a period of transition within the Belgian royal family. Princess Eléonore, 18, recently left for studies in the Netherlands, and Princess Elisabeth, the heir apparent, is preparing for her future role as queen. The appointment of a diplomat with extensive EU and UN experience may signal a continued focus on international engagement for Queen Mathilde.
What’s Next
Fostier will formally hand over her responsibilities to Steenbrugghe on 1 September 2026, while remaining available as an advisor. The specific domains in which she will continue to counsel the Queen remain to be clarified. The transition marks a significant moment for the Belgian royal household, closing a chapter of more than two decades of unwavering service.