Princess Antonia of Luxembourg (Antoinette Roberte Sophie Wilhelmine; 7 October 1899 – 31 July 1954) was a member of the Luxembourgish House of Nassau-Weilburg and the last Crown Princess of Bavaria as the wife of Crown Prince Rupprecht.

Born at Schloss Hohenburg, at Lenggries in Upper Bavaria, Antonia was the fourth daughter of Guillaume IV, Grand Duke of Luxembourg, who reigned between 1905 and 1912, and Marie Anne, a princess of the Portuguese House of Braganza.

She was the younger sister of two successive grand duchesses: Marie-Adélaïde and Charlotte. In the family she was called "Toni".

Antonia became the second wife of Rupprecht, Crown Prince of Bavaria. The two were engaged on 26 August 1918. At the time, Rupprecht was Generalfeldmarschall in the Imperial German army, and had successfully commanded the German Sixth Army at the Battle of Lorraine. This led to criticism of the close ties between the Luxembourgian Grand Ducal Family and the royalty of the German Empire at a time when Luxembourg was occupied by Germany. This added to the pressure already on Grand Duchess Marie-Adélaïde, who was forced to abdicate on 10 January 1919. Despite the abdication of her elder sister, and the overthrow of the Kingdom of Bavaria in favour of a republic, the two were married on 7 April 1921 at Schloss Hohenburg.

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