Ismaïl Omar Mostefai was identified after the successful identification of a finger found at the scene of the attack at Bataclan.
Mostefai had a criminal record, but he reportedly had not served time in prison.
The brother and father of Mostefai remain in police custody, while teams search their homes.
Mostefai’s older brother said he had not had seen or heard from his younger brother for several years.
"It’s crazy, insane," he told AFP news agency. "I was in Paris myself last night, I saw what a mess it was."
Investigations are continuing into the identities of the perpetrators and their accomplices, as well as those who were murdered in the seven attacks.
The 129 victims include three Chileans, two Mexicans, and a number of French and other European citizens.
