Bahrain's top court on Monday reduced the jail sentence of Shiite opposition leader Sheikh Ali Salman, who has been in prison since 2014, a judicial source said.
The Sunni-ruled kingdom's court of cassation reduced Salman's sentence from nine to four years, the source said on condition of anonymity.
The cleric, who headed the now-banned Al-Wefaq opposition movement, had been arrested on charges of inciting hatred and insulting the state in December 2014.
He was found guilty in July 2015 and sentenced to four years in jail.
An appeals court later more than doubled his jail term to nine years, after reversing an earlier acquittal on charges of calling for regime change by force.
Salman, 51, is considered a moderate who has pushed for a constitutional monarchy in Bahrain, unlike hardline groups who have demanded the toppling of the Sunni Al-Khalifa dynasty in a string of protests that go back to 2011.
Bahrain has cracked down over the past six years on dissent by members of the Shiite majority, whom it accuses of being manipulated by Iran.
The kingdom last year ordered the dissolution of the Shiite Al-Wefaq, the country's main opposition party, for "harbouring terrorism".
Al-Wefaq was the largest bloc in Bahrain's elected lower house of parliament. Its lawmakers resigned en masse in protest against the state crackdown on the 2011 protests