An apostille is a form of authentication issued to documents for use in countries that have signed the Hague Convention of 1961. This simplifies the process of verifying the legitimacy of public documents like birth certificates, diplomas, or power of attorney forms when they are being used in another country. For example, if you’re using a birth certificate from the U.S. in France, you will need an apostille attached to it, confirming that it is valid and legal.