Kim Kardashian is among those who argued that Cyntoia Brown should have been treated as a victim not a murderer.
Cyntoia Brown was 16 when she shot Nashville real estate agent Johnny Allen after he had taken her to his home for sex in 2004.
Brown, who was a runaway and under the influence of a violent pimp, said she shot Allen after he attacked her.
But she was convicted of first-degree murder and aggravated robbery and sentenced to life with the possibility of parole after serving at least 51 years in prison.
Now Tennessee Governor Bill Haslam has said Brown, who is now 30, had been given "too harsh" a sentence for the murder. She will be released on 7 August under the condition of a 10-year parole.
"Cyntoia Brown committed, by her own admission, a horrific crime at the age of 16," Mr Haslam said in a statement.
"Yet, imposing a life sentence on a juvenile that would require her to serve at least 51 years before even being eligible for parole consideration is too harsh, especially in light of the extraordinary steps Ms Brown has taken to rebuild her life."
Brown's case came to the attention of the public in a 2011 documentary about her case.
In a statement released by her attorneys, Brown thanked her supporters and the governor and promised to "do everything I can to justify your faith in me".
"My hope is to help other young girls avoid ending up where I have been," she added.
Since being jailed Brown has earned a high school diploma and is on track to complete her college education this year.
In a joint statement her lawyers Charles Bone and J Houston Gordon said her "transformation, when given the opportunity, is nothing short of miraculous".
They added: "She is truly a remarkable young woman with so much to offer this world and will now have that chance."
Reacting to the granting of clemency, Kim Kardashian, who has previously described Brown as a victim with "the courage to fight back," tweeted simply: "Thank you Governor Haslam."