Antoinette Roberte Sophie Wilhelmine, commonly referred to as Antonia, was the last Crown Princess of Bavaria before World War II. By birth, she was a member of the Luxembourgish House of Nassau-Weilburg as the child of Guillaume IV, Grand Duke of Luxembourg and Infanta Marie Anne of Portugal. Antonia was a survivor of the Sachsenhausen concentration camp.

William IV was Grand Duke of Luxembourg from 17 November 1905 until his death in 1912. He succeeded his father, Adolphe. Like his father, William mostly stayed out of politics despite being vested with considerable power on paper by the Constitution.