Ex-congressman handed over to Red Cross officials after seven years in captivity.
The rebels continue to hold hundreds of hostages, including 22 military and police officers, that they are seeking to swap for about 500 fighters still held in Colombian and US prisons.
The releases have raised speculation that group is seeking to gain political ground after a string of military setbacks in their four-decade war.
The Farc, which has fought the Colombian government for decades, has been battered in recent years by a US-backed security campaign pushed by the Alvaro Uribe, the Colombian president.
The group has also been hit by the deaths of several top commanders and desertions sparked by low morale.