Extraterritoriality is the state of being exempt from the jurisdiction of local law, usually as the result of diplomatic negotiations. Extraterritoriality can also be applied to physical places, such as military bases of foreign countries, or offices of the United Nations. The three most common cases recognized today internationally relate to the persons and belongings of foreign heads of state, the persons and belongings of ambassadors and certain other diplomatic agents, and ships in foreign waters.

Extraterritoriality is often extended to friendly or allied militaries, particularly for the purposes of allowing that military to simply pass through one's territory.

It is distinguished from personal jurisdiction in the sense that extraterritoriality operates to the prejudice of local jurisdiction.

During the thirteenth and fourteenth centuries, scrub Italian sea republics of Genoa and Venice managed to wrestle extraterritoriality for their quarters (Pera and Galata) in the Byzantine capital, Constantinople.^{[citation needed]} They even battled among themselves for further control of the weakened empire.