The House of Habsburg (; German pronunciation: [ˈhaːpsbʊʁk], traditionally spelled Hapsburg in English), 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.
A series of dynastic marriages enabled the family to vastly expand its domains to include Burgundy, Spain and its colonial empire, Bohemia, Hungary, and other territories. 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 18th century. The senior Spanish branch ended upon the death of Charles II of Spain in 1700 and was replaced by the House of Bourbon. The remaining Austrian branch became extinct in the male line in 1740 with the death of Holy Roman Emperor Charles VI, and completely in 1780 with the death of his eldest daughter Maria Theresa of Austria. It was succeeded by the Vaudemont branch of the House of Lorraine. The new successor house styled itself formally as the House of Habsburg-Lorraine (German: Habsburg-Lothringen), and because it was often confusingly still referred to as the House of Habsburg, historians use the unofficial appellation of the Habsburg Monarchy for the countries and provinces that were ruled by the junior Austrian branch of the House of Habsburg between 1521 and 1780 and then by the successor branch of Habsburg-Lorraine until 1918....LESS