Gino Strada, the founder of one of Italy's most prominent charities and builder of hospitals in war-torn countries, died on Friday aged 73, his medical charity Emergency said.
A surgeon and anti-war activist, Strada founded Emergency in 1994 to help civilian victims, providing healthcare in conflict zones around the world, including Iraq and Afghanistan.
He had recently suffered from heart problems, Italian media reported.
Since its first project in Rwanda in 1994, Emergency has treated around 11 million patients, the group's website says, working in 19 countries to set up hospitals and healthcare facilities.
A well-known public figure in Italy, Strada was sometimes touted as a possible minister, but his uncompromising anti-war and anti-racism ideas made him political enemies, especially on the right, and precluded him from office.
"He spent his life on the side of the weakest, working with professionalism, courage and humanity in the most difficult parts of the world," said Prime Minister Mario Draghi.
A critic of most Italian governments over their immigration and defence policies, Strada opposed Rome's military involvement in Iraq and Afghanistan and became a symbol of the country's pacifist movements.
His Twitter profile carries a quote from Albert Einstein: "War cannot be humanised. It can only be abolished."
Strada also decried Italian health policy, which he said favoured private clinics at the expense of quality public facilities for everyone.
Strada published his last newspaper article in the daily La Stampa on Friday about the advance of Taliban insurgents in Afghanistan, a country where he spent seven years, fiercely criticising the United States and the western powers.
"We said 20 years ago that this war would be a disaster for everyone. Today, the outcome of that aggression is in front of our eyes: a failure from every point of view," he wrote.
Strada's daughter Cecilia, a former president of Emergency, was not with her father at the time of his death because she was on board a boat rescuing migrants in the Mediterranean.
"I wasn't with him, but of all the places I could have been ... well, I was here ... saving lives. That's what my father and mother taught me".