Lon Lee Alle, from Singapore, was severely injured by a bite to his left leg, witnesses said.
The 50-year-old backpacker was reportedly visiting Komodo National Park in East Nusa Tenggara, the country's southernmost province, when the incident occurred on Wednesday.
Mr Alle was watching several of the large lizards eating pigs and goats belonging to villagers when he approached the animals to take photographs, according to local media.
He reportedly ignored repeat warnings from villagers that he should not get too close to the dangerous creatures.
“He must have been too close. A Komodo doesn’t like to be disturbed when eating,” park manager Sudiyono told The Jakarta Post.
Mr Alle was rescued by villagers and rushed to hospital on a military speed boat.
“This is the first incident of a human being bitten by a Komodo dragon in the past five years,” said Mr Sudiyono.
He added that the Singaporean had stayed with locals for three days before the incident to save money.
He said the incident occurred outside of the area set aside for tourists to observe Komodos.
“I also appeal to all tourists to take guides with you when wandering around to see Komodo dragons," he told journalists. "Never risk your safety by staying with locals and watching Komodos without an official guide only for the sake of your budget."
Komodo dragons are the largest species of lizard in the world and are found living in the wild only on a handful of small and remote Indonesian islands.
Every year tens of thousands of visitors travel to Komodo National Park to see the rare animals, which are closely related to the smaller, commoner monitor lizard.
Komodos can grow up to three metres in length and are strong enough to hunt and kill water buffalo.
It is often claimed that Komodos have a venomous bite; the animals have two glands in the lower jaw which secrete toxic proteins. It is believed these can cause bite wounds to become infected, gradually killing injured prey that escapes an initial attack.
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