A foreign national (i.e. a citizen that is not from the E.U or from the Schengen area) who decides to enter Italy must apply for an entrance visa through diplomatic representatives at the Italian consulate abroad. 

An entrance visa authorises a foreign national to cross borders and therefore, to enter Italian territory. It consists of a "sticker" that is applied to the passport or another valid identity document belonging to the applicant.  

The entrance visa is always required for stays that exceed 90 days. 

For stays that are less than 90 days, you should check if your country of origin is included in the Ministry of Foreign Affairs website database.