Marie-Adélaïde, Grand Duchess of Luxembourg, Marie-Adélaïde Thérèse Hilda Wilhelmine (June 14, 1894 - January 24, 1924) was a daughter of Grand Duke William IV of Luxembourg. Eldest of six sisters, she was proclaimed Heir Apparent on July 10, 1907 to solve the succession crisis. Thus, when her father died on February 25, 1912, she became the first reigning Grand Duchess of Luxembourg. She was also the first sovereign of Luxembourg since 1296 to have actually been born within the country.

She was highly interested in politics, and considering herself sovereign by the grace of God she did not refrain from intervening in the political life of the Grand Duchy. During World War I, she enjoyed a rather cordial relationship with the German occupiers, the root of harsh criticism after the liberation. Although not having done anything unconstitutional, voices in Parliament began to demand her abdication in January 1919. After consulting with the Prime Minister, she abdicated on January 14,1919 and was succeeded by her younger sister Charlotte.

Marie-Adélaïde entered a convent, taking the name "Sister Marie of the Poor", and died at Hohenburg Castle.