Rhys Bennett admitted to sexually assaulting and murdering Jill Barclay in Aberdeen on September 17, 2022 when he appeared at the High Court in Edinburgh on Wednesday.
The court heard that after he raped the 47-year-old woman, he poured gasoline on her and set her on fire.
He was jailed for life and told he must serve a minimum of 24 years before he is eligible to apply for parole.
In sentencing Bennett, Lord Arthurson said: “Her crimes against Mrs. Barclay were unimaginably wicked and indeed medieval in their barbarity.”
Mrs. Barclay leaves behind a partner and two children aged six and eight.
In a statement read out of court after the sentencing by Superintendent of Detectives Andrew Patrick, her family paid tribute to her as a “deeply loved life partner, mother and daughter.”
They added: “She did not deserve to die that day and especially in the unspeakable and brutal way that happened. This man has taken so much from us and changed our lives forever.”
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Bennett, 23, from Ballingry in Fife, appeared on the dugout wearing a gray tracksuit.
Prosecutor Lorraine Glancy KC told the court that forensic evidence suggested that Ms Barclay was alive when she was set on fire.
Bennett did not know her before the attack and met her while out at night.
He and his colleagues had been drinking at Spider’s Web pub in the Dyce area, where he met his victim.
He followed her as she made her way home, before launching an attack which, according to Lord Arthurson, “clearly involved extreme, sustained and frankly savage violence.”
At Farburn Gatehouse, he assaulted Mrs Barclay by repeatedly punching and kicking her, stomping on her head and body, and smashing her head into a downspout.
He then raped her, before pouring gasoline on her and setting her on fire.
Ms Glancy told the court that a man in the area that night heard “a high-pitched scream from a female voice, followed by her ‘no, no, no’ cry”.
Another woman told police she heard a woman’s scream, but after hearing it from her back garden for a while, she attributed it to guests at a nearby hotel.
In sentencing Bennett, Lord Arthurson told him: “The available evidence tells the horrible truth that your victim was still alive at the time the fire started.
“To be very clear: you burned her alive.”
Lord Arthurson said Mrs Barclay had lived a “full and active life” and told Bennett: “By her criminal behavior in this case, she took away her future and her family’s hopes and dreams in general.
“Their lives will never be the same. I have read most of the moving and articulate impact statements prepared by Mrs. Barclay’s partner, her eldest son, and her mother and aunt.
“Nothing this court can do, or I can say, today will compensate this family for their loss, and I fully understand that no court ruling could be enough in their eyes.”
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Bennett also admitted to trying to defeat the ends of justice by burning the clothes he was wearing and washing others.
He was given a term of punishment of 24 years for rape and murder, and four years for defeating the ends of justice, to be executed simultaneously.
He was also placed on the sex offender registry indefinitely.