A Grand Duchess is the wife of a Grand Duke or a woman who rules a Grand Duchy in her own right. The title of Grand Duchess is currently used by Maria Teresa Mestre, the consort of Grand Duke Henri of Luxembourg. Her mother-in-law Joséphine-Charlotte, whose husband abdicated in 2000, also used it until her death in 2005.

"Grand Duchess" is also the traditional translation of the title Velikaia Kniaginia, which was given to daughters and granddaughters of a Russian Tsar. It could more correctly be translated "Grand Princess". This title was also given to the wives of sons and grandsons of the Tsar where it was considered an actual title, not just a courtesy title. Several grand duchesses in Russia kept the title in their own right after the death of their husbands.

Styles

Most often, a reigning Grand Duke or Duchess was styled Royal Highness. Other members of the families differed in style. Junior members of the Grand Ducal Family of Luxembourg are also Royal Highnesses.

In Hesse-Darmstadt and Baden, however, junior members of the dynasty bore the style of Grand Ducal Highness (Großherzogliche Hoheit). For instance, prior to her marriage, Empress Alexandra of Russia was known as "Her Grand Ducal Highness Princess Alix of Hesse and the Rhine" (Ihre Großherzogliche Hoheit Alix Prinzessin von Hessen bei Rhein).

A Russian Grand Duke or Grand Duchess was an Imperial Highness.