Prison spokeswoman JoEllen Smith is cited as saying that Ariel Castro was found hanging in his cell at 9:30pm (2:30am UK time) last night.
Prison medical staff performed CPR before he was transported to a hospital, where he was pronounced dead, she said.
Castro was sentenced to life in prison plus 1,000 years after pleading guilty to 937 counts including kidnapping and rape.
An Ohio man who held three women captive for a decade, Ariel Castro, has been found dead in his cell, a prison official has told the Associated Press.
The official said he had committed suicide.
The house in which Ariel Castro kidnapped and held three women for over decade has been erased by Google.
The residence at 2207 Seymour Avenue has been blurred out on Google Street View.
Castro's home, dubbed the 'house of horror, was demolished earlier.
In attendance at the demolition was Michelle Knight, who was held captive by Castro for a decade.
Castro was sentenced to life in prison last week after pleading guilty to 937 counts including aggravated murder, rape and assault.
Michelle Knight told reporters gathered outside the property that abductees' mothers can have "strength" and "help" in dealing with the memories of the captivity.
Dramatic video has captured the demolition of Ariel Castro's Cleveland house - dubbed the 'house of horror' - where he held three Ohio women captive for a decade.
Castro was sentenced to life in prison plus 1,000 years last week.
The Cleveland house where Ariel Castro held three Ohio women captive for a decade is to be demolished today.
Castro was sentenced last week to life in prison plus 1,000 years.
One of the women who was imprisoned for years in the Cleveland home of Ariel Castro has written to local police officers thanking them for their work.
NBC News displayed a copy of the letter from Michelle Knight in which she writes that "life is tough, but I'm tougher".
Cleveland police posted the handwritten note on their Facebook page, but it has since been removed.
Two of the Cleveland kidnap victims detailed years of incarceration and abuse in personal diaries, a prosecutor has revealed.
In a sentencing memo file submitted last night, prosecutor Timothy McGinty said the diaries speak of "forced sexual conduct, of being locked in a dark room ... [and] of the dreams of someday escaping and being reunited with family".
Ariel Castro, who has pleaded guilty to 937 charges including rape and aggravated murder, is due to be sentence later today.
Three Cleveland women kidnapped and raped by former school bus driver Ariel Castro have said they are relieved and satisfied that he will spend the rest of his life in prison under a plea agreement with prosecutors.
Amanda Berry, 27, Gina DeJesus, 23, and Michelle Knight, 32, were abducted by Castro and held captive for as long as 11 years in his house, where he repeatedly raped them. They were rescued on May 6th, along with Berry's 6-year-old daughter fathered by Castro in captivity.
"Amanda, Gina, and Michelle are relieved by today's plea," the three women said in a statement released by the law firm Jones Day.
"They are satisfied by this resolution to the case, and are looking forward to having these legal proceedings draw to a final close in the near future."