Luke Prato, 25, dragged a terrified woman into a park and told her he intended to have sex with her. He was jailed for four years in March last year but, on Saturday, prison officers discovered him dead in his room.
Prato was moved from Exeter Prison to HMP Isle of Wight, a high security slammer for sex offenders, after he was classified as dangerous and vulnerable.
A prison service spokesperson said: "HMP Isle of Wight prisoner Luke Prato died on November 27.
"The Prisons and Probation Ombudsman has been informed."
An inquest will be held into his death at a later date, Devon Live reports.
The prisoner had a history of random acts of violence against strangers, a judge was told last year.
Exeter Crown Court heard Prato tried to "chat up" his 21-year-old victim on the dance floor of a pub earlier in the evening in 2019, but she told him to leave her alone.
He saw her walking home with a male friend a couple of hours later and shadowed them through the streets of Exeter, before attacking them both at the entrance to a park at 3am.
Prato set on the man first and once he had backed off he launched a sexual attack. He told the terrified victim, "I want you right now", and said he was going to have sex with her in the park as he thrust his hand up her skirt and groped her.
He grabbed her around the throat and tried to drag her into the park and fought off her friend when he tried to stop him, knocking him to the ground so violently he suffered a gash to his head.
The woman managed to escape and run across the road to try to seek refuge in a house but in the time it took for her to wake the owner, Prato followed her and attacked her again.
He was trying to drag her back towards the park with his hands around her throat when the householder opened her door and rushed out to rescue her.
Prato was eventually found guilty of sexual assault on the woman and causing actual bodily harm to her male friend.
sexual assault on the woman and causing actual bodily harm to her male friend