The House of Habsburg, also called House of Austria, was one of the most influential and outstanding royal houses of Europe. The throne of the Holy Roman Empire was continuously occupied by the Habsburgs between 1438 and 1740. The house also produced emperors and kings of the Kingdom of Bohemia, Kingdom of England ("Jure uxoris" King), Kingdom of Germany, Kingdom of Hungary, Kingdom of Croatia, Second Mexican Empire, Kingdom of Ireland ("Jure uxoris" King), Kingdom of Portugal, and Spain, as well as rulers of several Dutch and Italian principalities. From the 16th century, following the reign of Charles V, the dynasty was split between its Austrian and Spanish branches. Although they ruled distinct territories, they nevertheless maintained close relations and frequently intermarried. 

The House takes its name from Habsburg Castle, a fortress built in the 1020s in present-day Switzerland, in the canton of Aargau, 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 "Count of 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 Duchy of Austria. Rudolph had become King of Germany in 1273, and the dynasty of the House of Habsburg was truly entrenched in 1276 when Rudolph became ruler of Austria, which the Habsburgs ruled until 1918.
Where?
 King of Germany in 1273