In general, for documents originating in a foreign country to be valid in Italy it is necessary, as in most legal systems, that they undergo a process of recognition and validation by the Italian diplomatic and consular authorities abroad: this is called “legalisation”, whereby those authorities certify that the document in question was lawfully produced in its State of origin and its content is therefore reliable.
Given that legalisation is a procedure that involves an expenditure of time and resources that is hardly compatible with the requirements of modern commerce, most countries in the world - including Italy - have signed the Hague Convention of 5 October 1961 regarding the abolition of legalisation of foreign public documents.
This Convention means signatory nations have allowed legalisation to be replaced, as regards documents from another signatory nation, by the appending of an Apostille, rendering the document valid in the foreign country.
The Apostille is an attestation, prepared in accordance with a standard required by the Hague Convention, as to the legal qualification of the public official (or functiondedicates ary) who has signed the document and the authenticity of his or her seal or stamp.
This method means that a foreign national in possession of a document requiring validity in Italy can go to the authorities of the State in which it was issued - and a list of the appropriate authorities for each country is contained in the act of accession to the Convention itself - to have the apostille appended, thus making the document legally enforceable in Italy.
The national authority designated by Italy for issuing apostilles for Italian documents to be used abroad is the public prosecutor’s office for notarial deeds, for court documents and for those regarding civil status, while for administrative acts the competent office is the Prefecture (Territorial Government office) of the place where the document was issued.
Source: Italian Notarys' society (Consiglio Nazionale del Notariato)