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. Historians periodize the histories of many states and civilizations using a framework of successive dynasties, such as Ancient Iran, Ancient Egypt, and Ancient and Imperial China. The term "dynasty" may be used to delimit the era during which a family reigned. Before the 18th century, most dynasties throughout the world have traditionally been reckoned patrilineally, such as those that follow the Frankish Salic law. In polities where it was permitted, succession through a daughter usually established a new dynasty in her husbands family name. The word "dynasty" 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.

In summary, a dynasty is a series of rulers or leaders who are all from the same family, or a period when a country is ruled by them.