The Emperor of Austria (German: Kaiser von Österreich) was the ruler of the Austrian Empire and later the Austro-Hungarian Empire. A hereditary imperial title and office proclaimed in 1804 by Holy Roman Emperor Francis II, a member of the House of Habsburg-Lorraine, and continually held by him and his heirs until Charles I relinquished power in 1918. The emperors retained the title of Archduke of Austria. The wives of the emperors held the title empress, while other members of the family held the titles of archduke or archduchess.