CCTV footage of Lee Ferguson's assault in Wallsend in the early hours of February 19 shows Jade Jordan's torso and thighs ignite into a burst of yellow and orange flame.
Video taken from a police officer's body camera showed Miss Jordan lying on the ground on her back in the street, screaming in agony, with her clothing burnt off and clearly visible burns.
She spent three weeks in hospital after suffering deep burns to 13 per cent of her body, and needed surgery and skin grafts. She will be scarred for life around her stomach, abdomen and legs.
Ferguson, 32, of Bowness Avenue, Wallsend, admitted causing grievous bodily harm with intent, and sobbed in the dock as footage of his attack and the aftermath was played to the courtroom.
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Newcastle Crown Court heard the couple, who had been together for 12 years and have two children, have stayed together.
The court heard witnesses from a nearby pub heard Miss Jordan "shouting and then screaming" in the early hours, and saw the flames.
Ferguson, who stamped out the blaze and covered his victim in a coat to try to put out the flames, was heard saying 'I'm going to jail for a long time for this'.
Judge Robert Adams told him: "It seems to me the horror of what you had done and the injury inflicted became clear to you soon after you committed this offence.
"It is hard to imagine how painful those burns must have been.
"The pain and suffering at the time, which your offending caused, must have been extreme. There was extensive and deep burning."
The judge said the background to Ferguson's offending was his drinking vodka, arguments, smoking cannabis and him being jealous.
Prosecutor Paul Rowland told the court Miss Jordan did not make a statement about why or how she was attacked.
The court heard Ferguson filled a small bottle with accelerant, taken from a larger petrol can found inside his home, and used it in the attack. It was found at the scene.
Miss Jordan was taken to hospital in Cramlington before being transferred to the Royal Victoria Infirmary in Newcastle and later the regional burns unit.
Mr Rowland added: "An emergency operation was carried out. There was cleaning and dressing of the burns and also a laser scan undertaken. That showed burns to her legs and abdomen were deep. The consequences of that was grafting had to take place."
During two police interviews Ferguson denied responsibility, but he pleaded guilty when the case reached court.
John Wilkinson, defending, said Ferguson realises the effects of what he did on the victim and the family as a whole, and has sought help from professionals while in custody on remand.
He added: "I cannot and would not seek to explain his behaviour on that particular night. In many ways it is inexplicable. He was immediately aware of the enormity of what he had done. He has expressed genuine remorse for what has occurred."