An Apostille is a certificate attached to an official document (such as a birth or marriage certificate) that verifies:

The authenticity of the signature of the public official who signed the document,

The capacity in which that public official acted, and

The authenticity of the seal or stamp affixed to the document.

It is important to note that an Apostille does not verify or validate the contents of the document itself.

For a document issued in one country to be legally recognized in another, it must undergo a process of legalization (also called authentication). The 1961 Hague Convention Abolishing the Requirement of Legalization for Foreign Public Documents simplified this process for member countries. Under this agreement, countries that are signatories to the Apostille Convention recognize each other's official documents once an Apostille has been attached.

For countries not party to the Convention, document legalization is more complex and typically requires authentication by a consular official.

The term "Apostille" originates from the French verb "apostiller," which comes from the old French word "postille" meaning "annotation," and earlier from the Latin word "postilla."