Ukraine acknowledges that the ‘Ghost of Kyiv’ is a myth.

He shot down numerous Russian planes, survived enemy attacks and became a symbol of Ukraine’s surprisingly effective air defenses, earning a bold wartime moniker: The Ghost of Kyiv.

He is also, it turns out, a myth.

“The ghost of Kyiv is a superhero-legend, whose character was created by Ukrainians!” Ukraine’s Air Force Command wrote on Facebook on Saturday, dispelling a monthslong rumor — fueled by Ukrainian authorities themselves — that had invigorated the resistance to Russia’s invasion.

The Ukrainian statement came after some news outlets, including the Times of London, identified the Ghost of Kyiv as Major Stepan Tarabalka, an actual 29-year-old who died in an air battle in March. The claim echoed across social media and tabloid publications in Ukraine and the West, seeming to confirm that the story of the heroic fighter was real.

Instead, it has turned out to be one of the more successful pieces of propaganda in an information war that, at times, Ukraine has fought as fiercely as it has on the battlefield.

It was only a day after the beginning of Russia’s invasion that the Ukrainian media started reporting that an unknown pilot of a MIG-29 fighter jet had downed six enemy planes in 30 hours. Memes and illustrations started circulating online with the hashtag #ghostofkyiv, collecting hundreds of millions of views.

Even a former president of Ukraine, Petro O. Poroshenko, tweeted a picture of a pilot who he said was the Ghost of Kyiv and who had “six victories over Russian pilots!”

“With such powerful defenders, Ukraine will definitely win!” Mr. Poroshenko wrote. (The photo, it turned out, was from a 2019 Twitter post by the Ukrainian Defense Ministry.)

The Ukrainian government also joined in. On Feb. 27 it relayed on Twitter the story and the photo, calling the unknown pilot “a nightmare for invading Russian aircrafts.” It posted a video praising the pilot that included a clip from a combat flight simulator.

Around the same time, when the Ukrainian Defense Ministry announced on Facebook that dozens of discharged military pilots were returning to the Air Force, it referred to the fascination with the anonymous pilot: “Who knows, maybe one of them is the air avenger on the MIG-29.”

The stories proliferated and overlapped. After reports in early March that the Ghost of Kyiv had been shot down, Ihor Mosiychuk, a former Ukrainian lawmaker, reported that the pilot survived, went back to his base, took off in another jet and downed another enemy plane.

“The ghost is alive!” he wrote on Facebook. The Kyiv Post reported that he had destroyed as many as 49 planes.

Skepticism spread in some quarters. But the legend only grew. Artists produced NFTs, or nonfungible tokens, with the pilot’s image. Blue and gold “Ghost of Kyiv” fliers and illustrations circulated online.

On Friday, several publications identified the pilot as Mr. Tarabalka, an airman who died in battle on Mar. 13 and was posthumously awarded the military honor “Hero of Ukraine.” The Times of London also quoted Ukrainian sources as saying the pilot’s helmet and goggles were expected to go on sale at an auction in London.

The next day, the Air Force Command of Ukraine’s Armed Forces debunked the claims. “Hero of Ukraine Stepan Tarabalka is NOT ‘Ghost of Kyiv’ and he did NOT shoot down 40 planes,” it wrote on Facebook. But they still worked to keep the myth going.

“The #GhostOfKyiv is alive,” the Air Force wrote on Twitter. “It embodies the collective spirit of the highly qualified pilots of the Tactical Aviation Brigade who are successfully defending #Kyiv and the region.”

For many Ukrainians, that was all that mattered.

“He IS a legend,” Lesia Vasylenko, a Ukrainian lawmaker, wrote on Twitter, “He can’t be killed — he is a ghost.”