Suzerainty () is the rights and obligations of a person, state or other polity who controls the foreign policy and relations of a tributary state, while allowing the tributary state to have internal autonomy. While the subordinate party is called a vassal, vassal state or tributary state, the dominant party is called a suzerain. While the rights and obligations of a vassal are called vassalage, the rights and obligations of a suzerain are called suzerainty.

Suzerainty differs from sovereignty in that the dominant power allows tributary states to be technically independent, but enjoy only limited self-rule. Although the situation has existed in a number of historical empires, it is considered difficult to reconcile with 20th- or 21st-century concepts of international law, in which sovereignty is a binary concept, which either exists or does not. While a sovereign state can agree by treaty to become a protectorate of a stronger power, modern international law does not recognise any way of making this relationship compulsory on the weaker power. Suzerainty is a practical, de facto situation, rather than a legal, de jure one.