Wagner boss Yevgeny Prigozhin and his commander Dmitry Utkin were on board a plane that crashed north of Moscow, according to Russia's civil aviation authority.
Eight bodies have so far been found at the crash site by the Russian emergency services, according to the RIA state news agency.
Seven passengers and three crew were on board the Embraer aircraft and were all killed in the crash on Wednesday, the TASS news agency reported. The plane was heading from Moscow to St Petersburg.
Prigozhin, 62, and Wagner commander Utkin, 53, were among the passengers killed in the plane crash, according to a Telegram channel affiliated with the Wagner Group.
Russia's civil aviation authority also confirmed that the pair had been "on board" the jet.
The jet crashed near the village of Kuzhenkino, in the Tver region, 160 miles north of Moscow, Russia's emergency situations ministry said.
"An investigation has been launched into the Embraer plane crash that occurred tonight in the Tver region. According to the passenger list, among them is the name and surname of Yevgeny Prigozhin," Russia's Federal Air Transport Agency, Rosaviatsia, said on Wednesday.
Unconfirmed media reports suggest the business jet belonged to Prigozhin, but it was not immediately clear if he had boarded the flight.
Flight tracking data indicated that a private jet linked to Wagner and previously used by Prigozhin departed Moscow on Wednesday evening, only for its transponder signal to vanish within minutes.
The signal was lost in a remote area without nearby airfields suitable for a safe landing.
A photograph shared on a pro-Wagner social media account showed burning debris, with a partial tail number resembling that of a company-owned private jet.
The colour and placement of the number on the engine of the crashed jet match other photos of the Wagner aircraft examined by the Associated Press.
Wagner Group rebellion in Russia
Prigozhin led a short-lived mutiny against Russia's top military brass in June, and was described at the time by Vladimir Putin as a "traitor".
The Kremlin said his fighters would either retire, follow him there, or join the Russian military.
Once a close confidant of Vladimir Putin, Prigozhin often lambasted the likes of defence minister Sergei Shoigu and top general Valery Gerasimov in public addresses over their handling of the Ukraine invasion.
Prigozhin founded Wagner - a private military company whose fighters have deployed in support of Moscow's allies in countries including Syria, Libya and the Central African Republic - in 2014.
The US has sanctioned it and accused it of atrocities, which Prigozhin has denied.
Wagner boss posted video two days ago
Prigozhin was last seen in a video on Monday that appeared to have been shot in Africa, where he spoke about making the continent "free".
The Wagner Group boss released footage of himself speaking while wearing camouflage and holding a rifle.
Prigozhin also described how Wagner was tackling terrorist groups in the region and added that the group wanted to increase its presence in Africa.
He later shared details about Wagner's recruitment in the video, which was accompanied by a telephone number for those who wanted to join.
'He had crossed a line'
Former British intelligence officer Christopher Steele said this is not the first time he is believed to have been in Africa since his failed armed rebellion in June, and this sort of incident was "inevitable".
"It's very curious what he's been up to since 24 June when this revolt happened, and I think he had crossed the line," he told Sky News.
"I think this was almost inevitable."
Earlier, Mr Steele said a contract had been put out on Prigozhin by members of Russia's elite over the past few weeks.
Putin 'at concert' at time of crash
While reports are circulating that the boss of the Wagner Group has apparently been killed in the jet crash, the Russian president is at a concert.
The event is said to be dedicated to the 80th anniversary of Soviet troops' victory in the Battle of Kursk.
Meanwhile, Joe Biden has been briefed on the plane crash. The US president is currently on holiday in Tahoe Valley, California.
He said: "I don't know for a fact what happened but I am not surprised."
Biden added: "There is not much that happens in Russia that Putin is not behind."
A UK government spokesperson said: "We are monitoring the situation closely."
'Why didn't Prigozhin see this coming?'
Commenting on the crash, military analyst Sean Bell told Sky News: "After that abortive coup, I don't think any of us expected Prigozhin's life expectancy to be more than, I think we predicted, three months. It looks like it's two months."
Mr Bell said that following the unsuccessful Wagner Group mutiny, led by Prigozhin, many would have expected Vladimir Putin to "act very swiftly and decisively".
"Probably, because of the influence Prigozhin had, not only as an oligarch but as the leader of the Wagner Group, Putin would not want to make a martyr of him.
"Therefore there was a bit of tap dancing around what to do."
Mr Bell added: "The only question in my mind is why he didn't see this coming. He seemed to be still remaining in circulation.
"He turned up at the Russian Africa conference only a few weeks back and seemed to be on the same stage as President Putin. And yet what it appears now very clearly that his card was marked, his days were numbered. And it's no great surprise he's met an untimely end."
Professor David Lewis, an expert in global politics at the University of Exeter, also spoke to Sky News about the jet crash, and said: "This could be Putin's most ruthless revenge killing yet - and it will serve as a graphic warning."
But he added there will be "political consequences" as Prigozhin's death "will infuriate many of his own Wagner soldiers [and] a much wider group who are discontented with the current military leadership and saw Prigozhin as somebody who at least understood their concerns".