The US Department of Defense said on Monday that detainee Ridah Bin Saleh Al-Yazidi was repatriated from Guantanamo Bay to Tunisia.
It said 26 detainees remain at the facility, of which 14 are eligible for transfer.
Al-Yazidi, 59, was airlifted from the base in a secret operation that was completed 11 months after the Defense Department notified Congress that it had reached an agreement to return him to Tunisian custody, the Pentagon said.
It offered no details on the security arrangements surrounding his return.
Al-Yazidi was sent to the wartime prison the day it opened on Jan. 11, 2002.