The US president, Donald Trump suggests the pandemic, which began in 1918, brought an end to the conflict that lasted from 1939 to 1945.
Donald Trump has said the Spanish flu “probably ended the Second World War” – despite the conflict having started almost two decades later.
The US president incorrectly stated the pandemic began in 1917, one year before the first cases were reported in 1918.
Speaking at a White House news conference, Mr Trump suggested the illness had a bearing on the conclusion of the Second World War, which lasted from 1939 until 1945.
Mr Trump made the remarks while discussing the current coronavirus pandemic, which has seen more than 163,000 people in the US die with the virus.
The president was later escorted out of the briefing due to a shooting outside the White House.
Mr Trump said: “The closest thing is in 1917, they say, the great pandemic was a terrible thing where they lost anywhere from 50 to 100 million people.
“Probably ended the Second World War. All the soldiers were sick.”
The president continued: “It was a terrible situation and this [coronavirus] is highly contagious, this one is highly, highly contagious.”
A White House official later told USA Today that Mr Trump was talking about the First World War.
More people died from the Spanish flu than while fighting during that conflict, with the deployment of troops across the world thought to have helped it spread.
But most historians do not cite the pandemic as bringing an end to the First World War, which came to a close when Germany signed an armistice, having suffered huge numbers of casualties in battle as the strategic balance shifted decisively in the Allies’ favour.
While it is commonly known as Spanish flu, experts have since said it is more likely to have started in the US, UK, China or France.
It became commonly associated with Spain because the neutral country did not have wartime censorship that prevented reporting on the disease.
Mr Trump has faced criticism for his response to the COVID-19 outbreak, with critics claiming his downplaying of the disease and refusal to take stronger and swifter action has contributed to the US recording the highest death toll in the world.