Military occupation, also known as belligerent occupation or simply occupation, is the effective military control by a ruling power over a territory that is outside of that power's sovereign territory. The territory is then known as the occupied territory and the ruling power the occupant. Occupation is distinguished from annexation and colonialism by its intended temporary duration. While an occupant may set up a formal military government in the occupied territory to facilitate its administration, it is not a necessary precondition for occupation.

The rules of occupation are delineated in various international agreements, primarily the Hague Convention of 1907, the Geneva Conventions of 1949, as well as established state practice. The relevant international conventions, the International Committee of the Red Cross (ICRC) Commentaries, and other treaties by military scholars provide guidelines on such topics as rights and duties of the occupying power, protection of civilians, treatment of prisoners of war, coordination of relief efforts, issuance of travel documents, property rights of the populace, handling of cultural and art objects, management of refugees, and other concerns which are very important both before and after the cessation of hostilities. A country that establishes an occupation and violates internationally agreed upon norms runs the risk of censure, criticism, or condemnation. In the current era, the practices of occupations have largely become a part of customary international law, and form a part of the laws of war.