Belgium has extradited Paris attacks suspect Salah Abdeslam to face trial in France.
He was wounded and arrested in a dramatic raid in Brussels on 18 March after four months on the run.
The 26-year-old French national was born in Brussels and lived there before the Paris attacks.
Some 130 people were killed and dozens wounded in co-ordinated attacks carried out by so-called Islamic State in Paris on 13 November.
The federal prosecutor said Salah Abdeslam had been "surrendered to the French authorities this morning (in execution of the European Arrest Warrant issued by France on 19 March 2016)".
It is not immediately clear where he has been taken, although it is known that he was transferred recently from prison in Bruges to the high-security jail at Beveren, near Antwerp.
He was formally placed under arrest in France after his arrival at 09:05 local time (07:05 GMT) and would later come before investigating magistrates, prosecutors said. Prosecutors said they would seek his remand in custody while investigations proceeded.
Salah Abdeslam is charged with participation in terrorist murder and the activities of a terrorist organisation.
He was indicted by Belgian authorities last week over a shoot-out in the Forest area of Brussels in which four police were wounded, three days before he was arrested.
Earlier, French criminal lawyer Frank Berton told French media that he would be taking on Salah Abdeslam's defence in France following a two-and-a-half-hour meeting between the two last Friday at Beveren.
Berton described Salah Abdeslam as "falling apart because of the drama that unfolded in France" and said he wanted to explain his actions.
He said he was aware of the risks in representing his client, but insisted "he has the right to a fair trial".
But Mary also spoke disparagingly of his client, describing him as having the "intelligence of an empty ashtray".