The first page of the site featured a lengthy interview with Silvio Berlusconi under the headline "I, Silvio" in which the former prime minister criticised his successor Mario Monti and questioned the future of the euro.
The site is being run in partnership with Italian publishing group L'Espresso, publisher of left-leaning La Repubblica newspaper and L'Espresso weekly.
The editorial director is Lucia Annunziata, a former correspondent for La Repubblica who went on to become the head of the Rai public broadcasting giant.
"Italy and Europe are in economic turmoil.... It is into this maelstrom that the Huffington Post launches its Italian edition," Annunziata said in a statement that referred to the site as "a new civic space".
The editor-in-chief is Gianni Del Vecchio, a former editor of L'Espresso.
Greek-American author and columnist Arianna Huffington, editor-in-chief of The Huffington Post Media Group, was also in Italy for the launch.
She said she was pleased to be in a Mediterranean country "where someone is always trying to get you to eat something and nothing starts on time."
"While L'HuffPost will devote plenty of space to what isn't working in Italy, we will also put the spotlight on what is working: the innovation, ingenuity, spirit and resilience of the Italian people," Huffington said.
Berlusconi's former finance minister Giulio Tremonti, the head of Italy's largest metal workers union Maurizio Landini and the founder of gourmet group Eataly Oscar Farinetti were among the writers in the launch day line-up.
The flagship US edition of The Huffington Post receives some 36 million unique visitors a month, according to tracking firm comScore.