A dynasty is a sequence of rulers from the same family, usually in the context of a monarchical system, but sometimes also appearing in republics. A dynasty may also be referred to as a "house", "family" or "clan", among others.

Historians periodize the histories of many states and civilizations, such as the Roman Empire (27 BC – AD 1453), Imperial Iran (678 BC – AD 1979), Ancient Egypt (3100–30 BC), and Ancient and Imperial China (2070 BC – AD 1912), using a framework of successive dynasties. As such, the term "dynasty" may be used to delimit the era during which a family reigned.

Before the 18th century, most dynasties throughout the world were traditionally reckoned patrilineally, such as those that followed the Frankish Salic law. In polities where it was permitted, succession through a daughter usually established a new dynasty in her husband's family name. This has changed in all of Europe's remaining monarchies, where succession law and conventions have maintained dynastic names de jure through a female.

Dynastic politics has declined over time, owing to a decline in monarchy as a form of government, a rise in democracy, and a reduction within democracies of elected members from dynastic families.

Terminology

The word "dynasty" (from the Greek: δυναστεία, dynasteía "power", "lordship", from dynástes "ruler") is sometimes used informally for people who are not rulers but are, for example, members of a family with influence and power in other areas, such as a series of successive owners of a major company, or any family with a legacy, such as a dynasty of poets or actors. It is also extended to unrelated people, such as major poets of the same school or various rosters of a single sports team.