In some states, for example, an international driving license is required together with the driving license of your country, in others you must accompany your Italian driving license with a certified translation in English.
In almost all states and territories (with the exception of the Northen Territory), if you are a visitor you can drive with an Italian driving license, provided it is valid.
The rules then change when you get permanent residence.
To find out what the laws governing your guide in Australia are, you will find a summary of information on all states (NSW, QLD, SA, TAS, VIC, WA) and territories (ACT, NT). In each paragraph you will also find the link to the official site of the state or territory for further information on the case.
Australian Capital Territory
If you have a valid Italian or international driving license, you will not be asked for the ACT driving license. Visitors are considered to be those who are on vacation, traveling on business, students or workers who wish to leave Australia once their course of study or work experience is over, and young people with working holiday visa. In all these cases you can drive in the ACT with the Italian driving license accompanied by a certified translation (NAATI or AUSIT) in English or with the Italian driving license accompanied by an international driving license. Things change when residence in the ACT is obtained: after 3 months the state driving license becomes mandatory.
For more details, useful links and to find out what are the procedures to get the license in ACT or to obtain a certified translation of your Italian driving license click ACT.
New South Wales
You can drive in NSW with your Italian driving license if you are a tourist or a temporary visitor. However, your license must be accompanied by an English translation or an international driving license. If you wish, at the end of the third month of stay in the state you can request a document called Temporary Overseas Visitor license , but you are not obliged to do so. If you have your permanent residence right in the state of NSW, you can drive with your Italian driving license for a maximum of three months, at the end of which you will be asked for the NSW license.