He attended secondary school in Luxembourg and Switzerland, and received his baccalaureate in Grenoble in 1982.

Guillaume was presented the degree Doctor of Humane Letters, honoris causa, at Sacred Heart University's Academic Convocation and Induction of the Class of 2011 on 10 September 2007.

[1] On the night of 10 to 11 September 2000, Prince Guillaume and Princess Sibilla were involved in a serious car accident near Paris.

The transfer of the throne between his father Grand Duke Jean and his brother Henri was postponed from 28 September to 7 October.

12 June 1968, Neuilly-sur-Seine, France), the second child of French industrialist and patron of the Arts Paul-Annik Weiller (son of Paul-Louis Weiller and Aliki, Lady Russell) and Italian noblewoman Donna Olimpia Torlonia di Civitella-Cesi (daughter of Alessandro Torlonia, 5th Prince of Civitella-Cesi and Infanta Beatriz of Spain) and the second cousin of King Felipe VI of Spain[3] civilly in Sélestat on 8 September 1994 and religiously at Versailles Cathedral on 24 September 1994, who received the title "Princess of Luxembourg".