Taner Kilic is charged with supporting a US-based cleric who Ankara blames for a failed coup in 2016. His arrest was one of several cases that have raised concerns over Turkey's human rights record.
A Turkish court on Wednesday ordered the release of the local head of Amnesty International after more than a year in prison.
Taner Kilic was arrested in June 2017 on terrorism charges for allegedly having links to self-exiled Turkish cleric Fethullah Gulen, who Turkey blames for a failed coup in 2016.
Turkish prosecutors accuse Kilic of using ByLock, an encrypted messaging app that authorities claim was created specifically for Gulen's supporters. Amnesty denies the charges.
"We are overjoyed at this news. It has taken us more than a year of campaigning and struggle to get here, but Taner has finally been freed and is safely back at the arms of his wife and daughters," said Kumi Naidoo, Amnesty International's new secretary general.
Naidoo also tweeted a picture of Kilic hugging his family outside prison.
Amnesty said that although Kilic had walked free, charges against him and others, including its Turkey director Idil Eser, have not been dropped.
Naidoo said Amnesty will continue to display a "steely determination" in its fight for human rights in Turkey, where tens of thousands have been unjustly arrested as part of a crackdown targeting journalists, academics and human rights activists.
Rights groups have accused Turkey of using the crackdown, launched in the wake of the failed coup in 2016, to stifle dissent.
Kilic's verdict came a day after a court in the western province of Edirne released two Greek soldiers facing espionage charges in Turkey.
The court decisions come against the backdrop of escalating tensions between Turkey and the United States over the detention of an American pastor for terrorism charges.
Earlier on Wednesday, a Turkish court rejected an appeal for the vvangelical pastor, Andrew Brunson, to be released from house arrest and for his travel ban to be lifted.
ap/rc (Reuters, AFP, AP)