Eric Eoin Marques has been extradited to the United States.
The 33-year-old was this morning taken from the midlands prison and handed over to FBI agents at US immigration in Dublin Airport.
His extradition was sought by the US over allegations that he conspired to distribute and advertise child abuse images on the dark web.
He had previously launched a legal challenge aimed at halting his extradition, however the Supreme Court dismissed it.
The FBI believes he is the owner and administrator of an anonymous hosting site known as Freedom Hosting and the world's largest facilitator of the distribution of child abuse images.