A jury took four days to convict Marie Therese Kouao and her boyfriend Carl Manning in one of the most appalling cases of child cruelty heard by the Old Bailey.
Both defendants have been sentenced to life imprisonment.
Victoria Climbie was repeatedly beaten, burnt with cigarettes and scalding water, tied up and forced to sleep naked in a bath with only a bin liner to cover her.
Judge Richard Hawkins said: "What Anna [the name given on Victoria's false passport] endured was truly unimaginable. She died at both your hands, a lonely drawn out death".
Majority verdicts
Health Secretary Alan Milburn has ordered a statutory inquiry into the circumstances surrounding the case.
Social services and the police have been criticised for not stepping in to save Victoria, despite having several opportunities to do so.
Victoria died of hypothermia in February 2000 at the hands of Manning, 28, and her great aunt Kouao, 44, at their north London bedsit home.
Her body was covered in 128 injuries.
Manning denied murder but pleaded guilty to manslaughter and child cruelty.
Widowed Kouao, a French citizen, denied murder, manslaughter and cruelty to Victoria at the tiny studio flat the couple shared in Tottenham.
She claimed the little girl's death was due to witchcraft and denied all knowledge of cruelty.
Kouao put her hand over her mouth as the guilty verdicts - by a majority of 10 to two - were delivered.
Both defendants were also found guilty of child cruelty by unanimous verdicts.
Beaten and tied
The Home Office pathologist who examined her body, Doctor Nathaniel Cary, said it was the worst case of abuse he had seen in his career.
The Ivory Coast schoolgirl, was sent away by her family in 1998 in the hope of a better life.
"
It beggars belief how these two defendants could inflict such suffering on an eight-year-old child
"
Detective Inspector Keith Niven
Manning, a bus driver, believed she was Satan and beat Victoria with weapons including a bicycle chain and hammer.
He confessed to police: "You could beat her and she would not cry at all. She could take the beatings and pain like anything."
The court was told that Victoria was left tied up in the bath sometimes for more than 24-hours. One woman claimed Kouao told her she left Victoria there for "two or three days".
A church service to "cast out the devil" was planned for Victoria on the day she died.
'Horrific' evidence
Detective Inspector Keith Niven who led the investigation into Victoria's death said the jury had returned "a just and proper verdict".
"During the investigation I've been horrified by the evidence I have discovered," he said.
"It beggars belief how these two defendants could inflict such suffering on an eight-year-old child."
He said the police officers' thoughts were now with Victoria's parents whose world had been "turned upside down by the death of their beautiful girl".
In a statement Victoria's parents said: "We entrusted our daughter to an aunt because we are poor and she would have had the opportunity to live well and receive a good education.
"Unfortunately, she was the victim of tragedy. The spirit of our beloved daughter is now in the Ivory Coast and we want to begin our lives again for the sake of our other children."
During the trial, the court heard not only of Victoria's torture at the hands of her carers, but of the repeated failure by officials - police, social services and medical staff - to protect her.
Victoria was seen by medics at two London hospitals, covered in scars and fresh bruises and in one visit, with her scalp severely scalded.
Internal investigation
But after police and social services were contacted, it was decided Victoria suffered scabies and other injuries were accidental.
Victoria was sent home to live with her torturers.
Judge Hawkins said lessons had to be learned "about the failure of social services and police in this case".
Eight police officers in the child protection team are now the subject of an internal investigation.
And the statutory inquiry ordered by Alan Milburn will look at issues of health, housing, social services and policing surrounding the case.
The case has also been referred to the Police Complaints Authority.