Former Worldcom boss Bernard Ebbers has been sentenced to 25 years in jail for his part in the scandal which brought down the firm.
Mr Ebbers was found guilty of fraud and conspiracy in March, following revelations of an $11bn (£6.2bn) accounting fraud at Worldcom in 2002.
The 63-year-old was also guilty of seven counts of filing false documents.
The sentence was handed down by federal judge Barbara Jones, who earlier this week rejected his bid for a new trial.
The term effectively satisfies pleas from prosecutors for a life sentence to be imposed on Mr Ebbers.
Mr Ebbers will begin serving his sentence at a federal prison in Yazoo City, Mississippi, situated close to his home.
Defense lawyer Reid Weingarten had called for a more lenient sentence, given Mr Ebbers’ heart condition and his involvement in charitable works.
However, Judge Barbara Jones said she did not believe his heart condition was sufficiently serious to warrant a reduced sentence.
She also rejected his lawyers’ contention that the government overstated the losses that investors suffered in the fraud.
And she rejected their contention that Mr Ebbers was not a mastermind of the accounting wrongdoing.
Mr Ebbers “was clearly a leader of criminal activity in this case,” the judge said.
“A sentence of anything less would not reflect the seriousness of the crime.”
Worldcom’s collapse was the biggest bankruptcy in US corporate history.
Some 20,000 workers lost their jobs, while shareholders lost about $180bn, when the company filed for bankruptcy protection.
A former Worldcom salesman, Henry J Bruin Jr, told the hearing in Manhattan that the company’s collapse had caused him “untold human carnage” and that he had suffered “sheer hell”.
Mr Ebbers is the first of six former Worldcom executives and accountants facing sentencing this summer.
The remaining five have already pleaded guilty and agreed to co-operate in the case against their former boss.
On Monday, a judge backed a multi-million dollar settlement under which Mr Ebbers must surrender most of his personal assets, including $5m in cash, to resolve a shareholder lawsuit.
The settlement leaves Mr Ebbers’ wife with about $50,000 of her husband’s fortune, and a modest home in Jackson, Mississippi.
Worldcom emerged from bankruptcy last year and is now known as MCI.