Apostille is also a French word which means a certification. It is commonly used in English to refer to the legalization of a document for international use under the terms of the 1961 Hague Convention Abolishing the Requirement of Legalization for Foreign Public Documents. Documents which have been notarized by a notary public, and certain other documents, and then certified with a conformant apostille are accepted for legal use in all the nations that have signed the Hague Convention.
For example, when the will of an Australian decedent who had assets in Hong Kong is probated in Australia, if it then has to be presented in Hong Kong in order to transfer estate assets in Hong Kong to Australia, an Australian government apostille must be affixed to the following documents after notarization by an Australian Notary Public:
This is also true for the United Kingdom, which like Hong Kong is a signatory to the 1961 Hague Convention.
In countries which are not signatories to the 1961 convention and do not recognize the apostille, a foreign public document must be legalized by a consular officer in the country which issued the document. In lieu of an apostille, documents in the U.S. usually will receive a Certificate of Authentication.