There were 22 people on board in total - 15 people were rescued including a one-year-old childThe 56-metre-long luxury yacht, The Bayesian, had been moored off Porticello, east of Palermo, when the storm swept suddenly up the coast before dawn, tearing through beach clubs and little fishing ports.
Lynch's wife was among 15 people rescued after the luxury yacht sank amid violent winds and rains off the Sicily coast, according to Salvo Cocina of the Civil Protection Agency, leaving six others missing.
Italian authorities have opened a probe into the incident as the emergency response continued Monday.
Lynch, 59, was acquitted on all charges in a San Francisco court in early June after he was accused of the massive fraud linked to the sale of his software firm Autonomy to Hewlett-Packard.
He co-founded Autonomy in Cambridge in 1996.
US prosecutors accused Lynch of wire fraud and securities fraud, and conspiracy to commit offenses involving years of falsified records.
He had been extradited to the US from Britain to stand trial on the criminal charges.
A University of Cambridge graduate from Suffolk in eastern England, Lynch had disputed all charges and denied any wrongdoing. He was facing two decades in jail if convicted of the 17 charges.
A celebrated technology sector entrepreneur and investor, sometimes referred to as the UK's answer to Bill Gates, he had won numerous awards and plaudits in Britain and beyond.
A spokesperson for Invoke Capital, another firm he founded, declined to comment.
Lynch was reportedly on board the boat with colleagues from the company when the storm struck.
Following his US acquittal, he had been critical of his prosecution in the US.
He had told the BBC that the only reason he was free was "because I had enough money not to be swept away by a process that's set up to sweep you away".
"You shouldn't need to have funds to protect yourself as a British citizen", he said in the interview aired earlier this month.British businessman Mike Lynch, who is reportedly missing after the luxury yacht sank off the coast of Sicily, made his fortune in the IT industry.
Lynch co-founded software company Autonomy in Cambridge in 1996, which expanded rapidly to become one of the UK's leading tech firms.
His company's success led it to be being sold to computing giant Hewlett-Packard for $11bn (£8.6bn) in 2011 - a deal in which Lynch made £500m ($647m).
But the acquisition soon unravelled, as questions were asked about the enormous price tag.
Just a year later, HP wrote down the value of Autonomy to $8.8bn, saying Lynch had exaggerated its value.
Years of legal battles followed, which culminated in US prosecutors bringing charges against Lynch in 2018.
Prosecutors accused him of inflating the value of the firm by using backdated agreements to mislead about the company's sales, said he had concealed the firm's loss-making business reselling hardware, and also accused him of intimidating or paying off people who raised concerns.
But he was eventually extradited to the US in 2022 to face trial - a process which culminated in June with his acquittal.
In an interview with the BBC earlier this month, Lynch said "the reason I'm sitting here, let's be honest, is not only because I was innocent... but because I had enough money not to be swept away by a process that's set up to sweep you away".
