Mária Adelaida (full name Marie Adélaïde Theresia Hilda Antonia Wilhelmina) was Grand Duchess of Luxembourg between 1912 and 1919. She was the state's first female grand duchess, its first female ruler since Mária Theresa and its first ruler since János Vak (b. 1296), who was born on the land of Luxembourg. Mária Adelaida was born on June 14, 1894 in the Berg Castle in the city of Colmar-Berg. He was IV. He is the eldest child of Grand Duke William of Luxembourg (1852–1912) and Infanta Maria Anna of Braganza (1861–1942). As she had no younger brothers, the constitution was changed to allow female succession to the Luxembourg throne. Vilmos died on February 25, 1912, and Mária Adelaida took his place on the throne. He was only 17 at the time, and his mother was regent of the Grand Duchy until his 18th birthday a few months later. During his reign, he took an active role in the governance and political life of the state. He was a committed Catholic, and in his inauguration speech he called the growing social inequality the state's most important problem. After the outbreak of the First World War, the Grand Duchy declared itself neutral, but Germany did not take this into account and invaded the country on August 2, 1914. Because of this, after the war, Mária Adelaida was branded as a German supporter and forced to resign. After her resignation, she became a nun and died of influenza in 1924, aged just 29.

Grand Duchess Maria Adelaide was the ruler of Luxembourg from 1912 to 1919. During his reign, major changes took place in the Luxembourg coinage. In 1912, the new Luxembourg franc was introduced, consisting of 100 centimes. The previous Luxembourg coins were withdrawn from circulation after the war. The coins of Grand Duchess Marie Adelaida were as follows: 1 franc gold coin: The obverse of the coin shows the portrait of Grand Duchess Marie Adelaide, and the reverse shows the coat of arms of the Grand Duchy of Luxembourg. 5 franc gold coin: The obverse of the coin shows the portrait of Grand Duchess Marie Adelaide can be seen, and on the back the coat of arms of the Grand Duchy of Luxembourg and the year of the war, 1914.20 franc gold coin: The obverse of the coin shows the portrait of Grand Duchess Maria Adelaide, and on the reverse the coat of arms of the Grand Duchy of Luxembourg and the war year, 1915.50 franc gold coin: The obverse of the coin shows the portrait of Grand Duchess Maria Adelaide, and on the reverse, the coat of arms of the Grand Duchy of Luxembourg and the year of the war, 1916.100 franc gold coin: The obverse of the coin shows the portrait of Grand Duchess Mária Adelaida, and on the reverse, the coat of arms of the Grand Duchy of Luxembourg and the year of the war, 1917. In addition, silver and copper medals were minted during the reign of Grand Duchess Mária Adelaida. These coins depicted the coat of arms of the Grand Duchy of Luxembourg and the year of the war. The changes in Luxembourg coinage were one of the most important economic consequences of the reign of Grand Duchess Maria Adelaide. The new Luxembourg franc was retained after the war and is still the Luxembourg currency today.