Ghislaine Maxwell has been found guilty of recruiting and trafficking young girls to be sexually abused by the late American financier Jeffrey Epstein.
The 60-year-old was found guilty on five of the six counts she faced.
The verdict was reached after five full days of deliberation by a 12-person jury in New York.
It means the British socialite could spend the rest of her life behind bars.
Shortly after the verdict, her legal team said they were already working on an appeal.
US Attorney Damian Williams welcomed the verdict and commended the “bravery” of the victims who came forward.
“A unanimous jury has found Ghislaine Maxwell guilty of one of the worst crimes imaginable – facilitating and participating in the sexual abuse of children,” the statement said.
Maxwell, a longtime associate of convicted child sex offender Epstein, has been in jail since her arrest last July.
Epstein took his own life in 2019 while awaiting trial.
A well-connected socialite, she is said to have introduced Epstein to wealthy and powerful figures including Bill Clinton and Prince Andrew.
During the month-long trial, Maxwell’s lawyers argued that she was a scapegoat for Epstein’s crimes while prosecutors sought to link the duo as “partners in crime” who ran a “pyramid scheme of abuse”.
“Ghislaine Maxwell made her own choices. She committed crimes hand in hand with Jeffrey Epstein. She was a grown woman who knew exactly what she was doing,” Assistant US Attorney Alison Moe said.
It is not yet clear when Maxwell will be sentenced.