The House of Habsburg ( /ˈhæps.bɜrɡ/; ), also Hapsburg, and also known as House of Austria is one of the most important royal houses of Europe and is best known for being an origin of all of the formally elected Holy Roman Emperors between 1438 and 1740, as well as rulers of the Austrian Empire and Spanish Empire and several other countries.
The House takes its name from Habsburg Castle, a fortress built around 1020–1030 in present day Switzerland by Count Radbot of Klettgau, who chose to name his fortress Habsburg. His grandson, Otto II, was the first to take the fortress name as his own, adding "von Habsburg" to his title. The House of Habsburg gathered dynastic momentum through the 11th, 12th and 13th centuries.
By 1276, Count Radbot's seventh generation descendant, Rudolph of Habsburg, had moved the family's power base from Habsburg Castle to the Archduchy of Austria. Rudolph had become King of Germany/Holy Roman Emperor in 1273, and the dynasty of the House of Habsburg was truly entrenched in 1276 when Rudolph became sovereign ruler of Austria, which the Habsburgs ruled for the next six centuries.
A series of dynastic marriages enabled the family to vastly expand its domains, to include Burgundy, Spain, Bohemia, Hungary, and other territories into the inheritance. In the 16th century, the family separated into the senior Habsburg Spain and the junior Habsburg Monarchy branches, who settled their mutual claims in the Oñate treaty. The House of Habsburg became extinct in the male line in the 18th century. The Spanish branch ended upon the death of Charles II in 1700 and was replaced by the Anjou branch of the House of Bourbon in the person of his great-nephew Philip V.
The Austrian branch went extinct in the male person in 1740 with the death of Charles VI and in the female person in 1780 with the death of his daughter Maria Theresa and was succeeded by the Vaudemont branch of the House of Lorraine in the person of her son Joseph II. The new successor house styled itself formally as House of Habsburg-Lorraine (German: Habsburg-Lothringen), although it was often referred to as simply the House of Habsburg.