Diplomatic recognition in international law is a unilateral declarative political act of a state that acknowledges an act or status of another state or government in control of a state. Recognition can be accorded either on a de facto or de jure basis. Partial recognition can occur if many sovereign states refuse to recognize an entity as a peer. Recognition can be a declaration to that effect by the recognizing government or may be implied from an act of recognition, such as entering into a treaty with the other state or making a state visit. Recognition may, but need not, have domestic and international legal consequences. If sufficient countries recognise a particular entity as a state, that state may have a right to membership in international organizations, while treaties may require all existing member countries unanimously agreeing to the admission of a new member.

The Stimson Doctrine is the policy of nonrecognition of states created as a result of a war of aggression. The policy was implemented by the United States government, enunciated in a note of January 7, 1932, to the Empire of Japan and the Republic of China, of non-recognition of international territorial changes imposed by force. The doctrine was an application of the principle of ex injuria jus non oritur. Since the entry into force of the UN Charter, international law scholars have argued that states are under a legal obligation not to recognize annexations as legitimate, but this view is controversial and not supported by consistent state practice.