What is the country code for Italy dialing from US?

Writing an Italian number such as (06) 3444 5566 so that it can be dialled from the US would be +39 06 3444 5566.

From the US, dial the International Access Code 011, then the Country Code 39, then the area code such as 06 (*including* the zero), then the local number. (Italy is an exception to the general rule of dropping the leading zero of the area code when dialing internationally.)