Ali al-Ekry was among 20 medics, all Shi'ite Muslims, who were sentenced in September 2011 to prison terms ranging from five to 15 years, Reuters reported.
Most were cleared or given reduced sentences on appeal, including Ekry, a senior orthopaedic surgeon at Manama's Salmaniya hospital.
Bahraini lawyer Abdullah al-Shamlawi congratulated Ekry on his release in a tweet.
Since February 14, 2011, thousands of anti-regime protesters have held numerous demonstrations in Bahrain on an almost daily basis, calling on the al-Khalifa rulers to relinquish power.
In March that year, troops from Saudi Arabia and the United Arab Emirates, themselves repressive Arab regimes, were deployed to the country to assist Manama in its crackdown on protests. Hundreds of Bahraini activists have been imprisoned and suppressed.
On June 20, Bahraini authorities stripped Sheikh Qassim of his citizenship, less than a week after suspending the al-Wefaq National Islamic Society, the country’s main opposition bloc, and dissolving the Islamic Enlightenment Institution founded by Qassim, and the opposition al-Risala Islamic Association.
Over the past few weeks, demonstrators have held sit-in protests outside Sheikh Qassim’s home to denounce his citizenship removal.
Bahrain has also sentenced Sheikh Ali Salman, another revered opposition cleric, to nine years in prison on charges of seeking regime change and collaborating with foreign powers, which he has denied.
Sheikh Salman was the secretary general of the al-Wefaq National Islamic Society, which was Bahrain’s main opposition bloc before being dissolved by the regime.
Things actually seem to be getting worse. The country’s only remotely critical newspaper, Al Wasat, which was shut down in 2011, has now been ordered by the government to close its online edition too after criticizing the executions.