Stéphanie, Hereditary Grand Duchess of Luxembourg (born Countess Stéphanie Marie Claudine Christine de Lannoy on 18 February 1984), is the wife of Hereditary Grand Duke Guillaume, heir apparent to the throne of Luxembourg. She became engaged to the Hereditary Grand Duke on 26 April 2012 and married him, in a civil ceremony, on 19 October 2012, followed by a religious service the next day.

Stéphanie de Lannoy was born on 18 February 1984 in Ronse, East Flanders.^[1] She is the youngest child and fourth daughter of the eight children of Count Philippe de Lannoy (1922–2019) and Alix della Faille de Leverghem (1941–2012).^[1][2][3]

The House of Lannoy has been traced back to the 13th-century nobility of Hainaut, its members distinguishing themselves in military command and affairs of state. Those descended from Charles de Lannoy, 1st Prince of Sulmona, the victor of Pavia, held the title of Imperial count/countess from 1526.^[4]

Stéphanie attended the Dutch-language Sancta Maria de Ronse school and continued her education in Collège Saint-Odile in France. She then returned to Brussels for studies at L'Institut de la Vierge Fidèle, before taking up Russian language and literature in Moscow. She majored in German philology at the University of Louvain (UCLouvain) in Louvain-la-Neuve and also earned a master's degree at Humboldt University of Berlin.^[1] She is fluent in Dutch, French, English and German.^[5][6] She is able to speak a fair amount of Luxembourgish and Russian.^[7][8]

Hereditary Grand Duke Guillaume and Stéphanie dated for about two years prior to their engagement. The betrothal was announced on 26 April 2012.^[1] Distant cousins, they share multiple descents from the Austrian fieldmarshal Charles Marie Raymond, Duke of Arenberg.^[9] Their families are connected in several other ways: Stephanie's father, Count Philippe de Lannoy was a first cousin of Antoine, 13th Prince de Ligne, who married Princess Alix of Luxembourg — Guillaume's grand-aunt — their son Prince Antoine Lamoral married Countess "Minthia" de Lannoy, Stephanie´s second cousin once removed. Count Philippe was also a first cousin of Princess Yolande de Ligne, who married Archduke Carl Ludwig of Austria, and their child, Archduke Carl Christian of Austria (Stephanie's second cousin) married Princess Marie Astrid of Luxembourg, Guillaume's aunt.

Countess Stéphanie and the Hereditary Grand Duke married in a civil ceremony at the Town Hall, on 19 October 2012. Their religious wedding took place on 20 October 2012 at the Cathedral of Our Lady of Luxembourg.^[10] The bride wore a dress designed by Elie Saab and the Lannoy family tiara. The bridal attendants were the bridegroom's sister Alexandra and nephew Gabriel, and the bride's nieces and nephew: Antonia and Madeleine Hamilton, Caroline and Louise de Lannoy, and Isaure and Lancelot de le Court.^[11]

Since June 2012, Hereditary Grand Duchess Stéphanie has been a member of the board of directors of the Fondation du Grand-Duc et de la Grande-Duchesse.^[12] Since January 2016, she is The Grand Duke Jean Museum of Modern Art’s chair of the board.^[13][14]

She granted her patronage to the Les Amis des Musées d’art et d’histoire du Luxembourg association, the Scienteens Lab,^[15] and to the Blëtz asbl, a Luxembourg association that aims to help those affected by stroke. Since May 2017, she holds the position of honorary president and administrator of the De Mains de Maîtres association.^[15]

Born Countess de Lannoy, Stéphanie has been styled as "Her Royal Highness The Hereditary Grand Duchess of Luxembourg" since her marriage. Her full title and style is: "Her Royal Highness Princess Stéphanie Marie Claudine Christine, Hereditary Grand Duchess of Luxembourg".