The total population fell by 189 000 to 60.25 million, the fifth straight year of decline, meaning that since 2014 Italy has lost some 551 000 residents, roughly the equivalent of its sixth largest city, Genoa.
Italy's economy has barely grown in the last 20 years and stagnant wages and poor job prospects are widely blamed for Italians' reluctance to have babies and the exodus abroad of its young people.
The country's economic situation has worsened dramatically this year due to the coronavirus emergency, with gross domestic product forecast to fall by around 10%.
The minister for families, Elena Bonetti, called the latest ISTAT data "shocking" and said it showed "the terribly high cost that young generations have had to pay in terms of hope for the future and personal fulfilment."
But for migrant arrivals in Italy, the drop in the resident population would have amounted to some 844,000 in the last five years, the equivalent of its fourth largest city, Turin.
The number of Italians moving abroad rose 8.1% year-on-year, in 2019, while immigrant arrivals declined by 8.6%.
Foreigners accounted for 8.8% of the resident population at the end of last year, meaning Italians amounted to 54.9 million.