The judge said Derek Shovin’s conviction was based on “his abuse of a position of trust and authority and the particular cruelty he showed Mr. Floyd”.
Mr Floyd, 48, died nine minutes after Chauvin knelt on his neck.
His death sparked worldwide protests against racism and police brutality.
Chauvin, 45, was convicted last month of second-degree murder and other charges. At his trial, his lawyer described the killing as a “well-intentioned mistake”.
Chauvin was also forced to register as a predatory felon and banned from owning firearms for life.
He and three other former police officers were charged with violating George Floyd’s civil rights.
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The last 30 minutes of George Floyd’s life
The Floyd family and their supporters welcomed the verdict.
“This landmark verdict brings the Floyd family and our nation one step closer to healing by providing closure and accountability,” tweeted lawyer Ben Crump.
Mr Floyd’s sister, Bridget Floyd, said the ruling showed the issue of police brutality was “finally being taken seriously” but that there was “still a long way to go”.
President Joe Biden said the verdict “seems appropriate” but admitted he did not know all the details.
At the sentencing hearing, Mr Floyd’s brother, Terrence Floyd, asked for the maximum possible sentence, which is 40 years.
“Why, what were you thinking, what was going through your mind when you put your knee on my brother’s neck?” He said.
Mr. Floyd’s daughter Gianna, 7, appeared in a video and said she missed him and loved him.
“I ask about him a lot,” she said, “‘My dad used to brush my teeth.'”
The judge said the case was painful for the community and the country, but especially for Mr Floyd’s family.
“The judgment is not based on emotion, not based on sympathy, but at the same time I want to acknowledge the deep and great pain that all families feel, particularly the Floyd family,” Justice Peter Cahill said.
Chauvin told the court he offered condolences to the Floyd family and said “there will be more information in the future” and that he hoped “things will be reassuring”.
However, he did not apologize.
In court, Chauvin’s mother said he was a “good person”.
“I have always believed in his innocence and I will never waver from that,” Carolyn Pawlenty said.
Minnesota Attorney General Keith Ellison said Chauvin’s sentence was “one of the longest ever imposed on a former police officer for use of deadly force.”
What happened to George Floyd?
In May 2020, he bought a pack of cigarettes at a convenience store. An employee believed he had used a counterfeit note and called the police after Mr Floyd refused to return the cigarettes.
When police arrived, they ordered Mr. Floyd out of his parked car and handcuffed him. When the officers tried to get the screaming Mr. Floyd into their patrol car, an argument broke out. They threw him to the ground and pinned him to the ground under his own weight.
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Chauvin held Mr. Floyd’s knee in the neck for more than nine minutes.
While restrained, Mr. Floyd said more than 20 times that he could not breathe, pleaded with his mother and begged “please, please, please.”
When the ambulance arrived, Mr. Floyd was motionless. An hour later he was pronounced dead.
His death was filmed by Darnella Frazier, now 18, who saw him walking with his cousin when he was arrested.
She said she started recording the incident on her phone because “I saw a man who was scared and begging for his life”.
Earlier this month, Ms. Fraser was awarded a special prize from the Pulitzer Prize, the most prestigious award in American journalism.