A patient diagnosed with pneumonia near Paris on 27 December actually had the coronavirus, his doctor has said.
This means the virus may have arrived in Europe almost a month earlier than previously thought.
Dr Yves Cohen said a swab taken at the time was recently tested, and came back positive for Covid-19.
The patient, who has since fully recovered, said he had no idea where he caught the virus as he had not been to any infected areas.
Knowing who was the first case is key to understanding how the virus spread.
What do we know about the new case?
Dr Cohen, head of emergency medicine at Avicenne and Jean-Verdier hospitals near Paris, said the patient was a 43-year-old man from Bobigny, north-east of Paris.
He told the BBC's Newsday programme that the patient must have been infected between 14 and 22 December, as coronavirus symptoms take between five and 14 days to appear.
Listen to the interview here
He was admitted to hospital on 27 December exhibiting what later became to be known as the main coronavirus symptoms, including a dry cough, a fever and trouble breathing.
This was four days before the World Health Organization's China country office was informed of cases of pneumonia of unknown cause being detected in the Chinese city of Wuhan.
The patient, Amirouche Hammar,told French broadcaster BFMTV that he had not travelled before falling sick.
Dr Cohen said two of the patient's children had also fallen ill but that his wife had not shown any symptoms. But Dr Cohen pointed out that the patient's wife worked at a supermarket near Charles de Gaulle airport and could have come into contact with people who had recently arrived from China.
The patient's wife said that "often customers would come directly from the airport, still carrying their suitcases".
"We're wondering whether she was asymptomatic," Dr Cohen said. He called for the potential link to be investigated further.