Prime Minister Giuseppe Conte said that people would only be permitted to travel for work or family emergencies.
He said the measures, which come into effect on Tuesday, were to defend the most fragile members of society.
Italy's coronavirus death toll jumped on Monday by 97 to 463. It is the worst-hit country after China.
The number of confirmed infections also increased to 9,172, up from 7,375 on Sunday, official figures show.
Cases of the virus have been confirmed in all 20 Italian regions.