Habsburg Monarchy (German: Habsburgermonarchie), or Danubian Monarchy (German: Donaumonarchie), or Habsburg Empire (German: Habsburgerreich) is a modern umbrella term coined by historians to denote the numerous lands and kingdoms of the Habsburg dynasty, especially for those of the Austrian line. The historiographic terms Austria, Austrian and Austrians are frequently used as pars pro toto shorthand referring to the Habsburg Monarchy. From 1438 to 1806 (with the exception of 1742 to 1745), a member of the House of Habsburg was also Holy Roman Emperor. However, the states of the Holy Roman Empire ruled by their own dynasties (and over which the emperor exercised only very limited authority) are not considered to have been part of what is now called the Habsburg Monarchy.

The history of the Habsburg Monarchy begins with the election of Rudolf I as King of Germany in 1273 and his acquisition of the Duchy of Austria for his house in 1282. In 1482, Maximilian I acquired the Netherlands through marriage. Both territories lay within the empire and passed to his grandson and successor, Charles V, who also inherited Spain and its colonies and ruled the Habsburg empire at its greatest territorial extent. The abdication of Charles V in 1556 led to a broad division of the Habsburg holdings between his brother Ferdinand I, who had been his deputy in the Austrian lands since 1521, and the elected king of Hungary and Bohemia since 1526, and his son Philip II of Spain. The Spanish branch (which held all of Iberia, the Netherlands, Burgundy, and lands in Italy) became extinct in 1700. The Austrian branch (which also had the imperial throne and ruled Hungary, Bohemia, and all the crowns entailed to them) was itself divided between different branches of the family from 1564 to 1665 but thereafter remained a single personal union.

The Habsburg Monarchy was thus a union of crowns, with no single constitution or shared institutions other than the Habsburg court itself, with territories inside and outside the Holy Roman Empire that were united only in the person of the monarch. The composite state became the most common dominant form of monarchies in the European continent during the early modern era. A unification of the lands of the Habsburg Monarchy took place in the early 19th century, when the Habsburg possessions were formally unified in 1804 as the Austrian Empire, which in 1867 became the Austro-Hungarian Empire and survived until 1918. It collapsed following defeat in the First World War.

In historiography, the Habsburg Monarchy (of the Austrian branch) is often called "Austria" by metonymy. Around 1700, the Latin term monarchia austriaca came into use as a term of convenience. Within the empire alone, the vast possessions included the original hereditary lands, the Erblande, from before 1526; the lands of the Bohemian crown; the formerly Spanish Netherlands from 1714 until 1794; and some fiefs in Imperial Italy. Outside the empire, they encompassed all the lands of the crown of Hungary as well as conquests made at the expense of the Ottoman Empire. The dynastic capital was Vienna, except from 1583 to 1611, when it was in Prague.