Ghislaine Maxwell has appealed against her child sex trafficking conviction and the 20-year prison term she was handed by a US judge last month.
Maxwell, 60, was convicted in December of recruiting and trafficking four teenage girls for abuse by her then-boyfriend Jeffrey Epstein.
Epstein took his own life in a New York jail cell in 2019 while awaiting his own trial.
Maxwell's appeal process was expected and will likely last several months.
During her trial, her lawyers argued that she was being scapegoated for Epstein's crimes, calling her friendship with the financier the "biggest mistake of her life".
Judge Alison J Nathan rejected attempts to throw out the case, including after Maxwell's lawyers argued that one juror had failed to inform the court that he had been abused as a child.
She also rejected arguments that Maxwell had not been allowed to prepare adequately for her trial, and that prosecutors had waited too long to bring their case against her.
Pronouncing the sentence in June, Judge Nathan said Maxwell's conduct had been "heinous and predatory" and that she "played a pivotal role" in Epstein's abuse.
As well as jail time, the judge imposed a fine of $750,000 (£610,000).
Her lawyer had asked for a sentence of no more than five years.
It remains unclear on what grounds Maxwell plans to appeal. Her lawyers were not required to give a reason in Thursday's legal filing.
Addressing her victims in the Manhattan courthouse in June, Maxwell said she empathised with them, adding that she hoped her prison sentence would allow the victims "peace and finality".
Maxwell has been in custody since her arrest in July 2020, held mostly at Brooklyn's Metropolitan Detention Center.
The case against the British former socialite has been one of the highest-profile since the emergence of the #MeToo movement, which encouraged women to speak out about sexual abuse.
The crimes of Epstein, who mixed with some of the world's most famous people, were first reported in the media in 2005 and he served prison time in Florida in 2008-09 on a state charge of procuring a minor for prostitution.
Following numerous lawsuits, he was arrested again in 2019 in a federal case in New York.
At least eight women wrote letters to Maxwell's judge during her trial describing how they had suffered.