A Dublin man faces at least 15 years in US prison after pleading guilty to a child pornography offence.
33-year-old Eric Eoin Marques - a dual US-Irish citizen - was extradited by Irish authorities last year to face federal charges in Maryland.
Authorities in the US said he has now pleaded guilty to conspiracy to advertise child pornography on the dark web.
If the plea agreement is accepted by the court, Marques could be sentenced to between 15 and 21 years in prison.
Marques had been accused of operating a free, anonymous web hosting service between 2008 and 2013.
Authorities claimed the hosting service contained over 8.5 million images of child exploitation - including 1.97 million images/videos involving victims that were not known to authorities.
Robert Hur, Attorney for the District of Maryland, announced the guilty plea yesterday.
He said: “This is an egregious case where one individual facilitated the abuse of more than a million new child victims and attempted to keep the abuse hidden on the dark web.
"We must do everything we can to bring individuals like Marques to justice in order to keep our children safe.”
Marques is due to be sentenced in May.
The Dublin man's surrender to US authorities was approved in 2015, but was not executed until last year to allow him to appeal the decision.
The five judges who heard his case at the Supreme Court all ruled against him.
FBI Special Agent Brooke Donahue had previously travelled to Ireland to give evidence at Marques' extradition hearing.
He told the High Court that Marques was suspected of being “the largest facilitator of child pornography websites on the planet".