A dynasty is a succession of rulers who belong to the same family for generations. A dynasty is also often called a "house", e.g. the House of Saud or House of Habsburg. In the histories of Europe, much of Asia and some of Africa, ruling and noble houses have usually been patrilineal; inheritance and kinship being predominantly viewed and legally calculated through descent from a common ancestor in the male line. Often, however, if the male lineage died out, descendants through females (and sometimes the females themselves) were recognized as entitled to inherit the dynasty's realms and/or wealth.

The term "dynasty" is also used to explain the era during which a family reigned, as well as events, trends and artifacts of that period, e.g. "Ming dynasty vase". In such cases, often the "dynasty" is dropped but the name may be used adjectivally, e.g. "Tudor style", "Ottoman expansion", "Romanov decadence". Historians traditionally consider a state's history within a framework of successive dynasties, particularly with such nations as China, Ancient Egypt, Vietnam and the Persian Empire. Much of European political history was dominated, successively and together, by dynasties such as the Carolingians, the Capetians, the Habsburgs, the Stuarts, the Hohenzollerns and the Romanovs. Until the nineteenth century, it was taken for granted that a legitimate function of a monarch was to aggrandize his dynasty, that is, to increase the territory, wealth and power of family members.

Dynastic names may not be the same as individual surnames, in that titles are customarily used instead. Or the name of the dynasty may follow the throne by descending through females, e.g. the current heads of the dynasties of Grimaldi, Habsburg, Orange and Romanov actually descend paternally from, respectively, the houses of Polignac (Chalençon), Lorraine, Lippe and Oldenburg. Also, often a new dynastic name does not signal an altogether different family, so much as a new branch of the dynasty that has obtained the throne: kings of the House of Anjou, Bourbon, Valois and Burgundy dynasties were all male-line descendants of Hugh Capet of France and are collectively called Capetians. Thus, by a royal decree of 1960 the British ruling dynasty remains the House of Windsor, despite the present Queen having married Philip Mountbatten, who is by birth a prince of the reigning Danish dynasty of Schleswig-Holstein-Sonderburg-Glücksburg, itself a branch of the House of Oldenburg, of which the Romanovs descended from Peter III were also agnatic descendants.

Dynasties may change due to war, but also when a king fails to produce an heir, sometimes resulting in a maternal relative's succession. The dynasty usually then takes the name of that successor's paternal family name.