A constituent state is a state entity that constitutes a part of a sovereign state. A constituent state holds regional jurisdiction over a defined administrative territory, within a sovereign state. Government of a constituent state is a form of regional government. Throughout history, and also in modern political practice, most constituent states are part of complex states, like federations or confederations. Constituent states can have republican or monarchical forms of government. Those of republican form are usually called states or autonomous states, republics or autonomous republics, or cantons. Those that have a monarchical form of government are often defined by traditional hierarchical rank of their ruler (usually a principality, or an emirate).
Constituent states united in a federal union under a federal government are more specifically known as federated states. There are numerous historical examples for constituent states within various federations. In modern political practice, among most notable examples are U.S. states and constituent entities of the Russian Federation.