The ruling by U.S. District Judge Paul G. Gardephe in New York was another crushing blow for Avenatti, 50, who was once one of the most familiar faces on cable TV news as the representative of former porn star Stormy Daniels.
Speaking through sobs, Avenatti said that he was truly sorry for the pain he has caused and that he had betrayed his values, his profession and his family.
"I will never have the privilege of practicing law again. I am deeply humbled before you today. I have destroyed my career, my relationships and my life," he told the court.
"Every father wants their children to be proud of them. I want mine to be ashamed. Because if they are ashamed, it means their moral compass is exactly where it should be," he said.
Avenatti admitted that he let the power of celebrity get the better of him.
"When I was a child, I dreamed about becoming a lawyer, doing good and pursuing justice and fighting for the little guy. I did just that, and then I lost my way," he said. "Why did this need to happen? All the fame and notoriety is meaningless. I am truly sorry for all the pain I have caused, and I am deeply humbled before you today."
Gardephe noted that Avenatti had no previous criminal record, but he said his conduct in this case was "outrageous."
Avenatti "hijacked his client's claims, and he used those claims to further his own agenda, which was to extort millions of dollars from Nike for himself," Gardephe said.
Avenatti, who is scheduled to surrender Sept. 15, will have to serve three years of supervised release after he gets out of prison.
U.S. Attorney Audrey Strauss said: "Michael Avenatti used illegal and extortionate threats and betrayed one of his clients for the purpose of seeking to obtain millions of dollars for himself.
"Not only did Avenatti attempt to weaponize his law license and celebrity to seek to extort payments for himself, he also defrauded his own client. Avenatti will now serve substantial time in prison for his criminal conduct."
After a three-week trial, Avenatti was convicted in February 2020 of extortion, transmission of interstate communications with intent to extort and wire fraud in connection to threats he made against Nike, the sports equipment and apparel giant.
When federal agents arrested Avenatti in March 2019, he had been representing a Los Angeles youth basketball coach who was alleged to have information that Nike employees made illicit payments to top high school athletes.
Avenatti had threatened to ruin Nike's reputation and crater its stock price unless it agreed to pay him and his client millions of dollars, prosecutors said.
He was caught on a recorded call hurling expletives as he pressured Nike representatives to pay him.
"I'm not f---ing around with this, and I'm not continuing to play games," Avenatti told Nike reps, according to court papers. "You guys know enough now to know you've got a serious problem. And it's worth more in exposure to me to just blow the lid on this thing. A few million dollars doesn't move the needle for me."
Prosecutors say he demanded that Nike pay his client $1.5 million and compensate him and his co-conspirator $15 million to $25 million to conduct an "internal investigation" for the company.
Avenatti's defense attorneys had asked for a six-month prison term, noting that his crimes were not violent and that no one was defrauded of any money.
"He cannot go anywhere in public without inducing and subjecting himself to vitriolic comments and abuse," his attorneys wrote.
Prosecutors said Avenatti deserved a "very substantial" prison sentence of eight years for having callously used his high-profile persona to "enrich himself."
"This was an egregious abuse of trust, and it warrants real and serious punishment," prosecutors wrote.
His legal problems still aren't done, as he is set to go on trial next year in federal court accused of having defrauded Daniels out of hundreds of thousands of dollars she was owed for a book deal.
Avenatti also faces other federal fraud charges in Los Angeles. Prosecutors allege that between 2015 and 2019 Avenatti stole almost $10 million in settlement funds from at least five clients, including one who is paraplegic. He has pleaded not guilty to all charges.