Peter's Square in the Vatican yesterday and suffered serious burns, officials said.
The man entered the square with a bottle of petrol early in the morning, doused himself, and lit a flame.
A Jesuit priest passing by tried to put out the flames with his cape before police arrived with a fire extinguisher. Two policemen suffered slight burns to their hands and smoke inhalation.
The man, who was taken to hospital with serious burns on his torso, was carrying a note with his daughter's phone number on it. His reasons for setting himself alight were not known and the contents of the note were not disclosed.
Pope Francis was in his residence in another part of the Vatican at the time.
Meanwhile, the Vatican has hired two big international consulting firms to improve financial accounting procedures and streamline media operations in its latest bid to clean up often murky finances and improve efficiency by cutting through red tape.
Pope Francis has already set up three commissions to advise him on what to do with the troubled Vatican bank, how to reform the administration and to address sexual abuse of children, a scandal that tainted his predecessor Benedict XVI's incumbency.
The Vatican said yesterday it had hired KPMG to "align the accounting procedures of all departments of the Holy See to meet international standards".