The secretary general of Bahrain's Islamic Action Society, also referred to as Amal Party, has been released after serving five years behind bars in the tiny Persian Gulf kingdom.
The Arabic-language Bahrainmirror website reported the release of Sheikh Mohammed Ali Mahfouz on Saturday.
A Bahraini court had sentenced Mahfouz to 10 years in prison, but the court of appeal ruled in November 2012 to reduce his jail term to five years.
Mahfouz was imprisoned over a complaint by the minister of justice against Amal Party.
Anti-regime protesters have been holding rallies across Bahrain since mid-February 2011, calling on the ruling family to relinquish power.
The Al Khalifah regime is engaged in a harsh crackdown on dissent and widespread discrimination against the country's Shia-majority. Scores of people have been killed and hundreds of others injured or arrested in the tiny Persian Gulf kingdom.
Rights groups have repeatedly blasted Manama for handing down long-term sentences to anti-regime activists.
Bahrain, a key US ally in the Middle East, hosts the Fifth Fleet of the US Navy.