While the Public Prosecution did not name Rajab on a statement carried on the official news agency announcing a trial on Oct. 19, the Interior Ministry identified him when he was arrested on Oct. 2.
Rajab took a leading role in the 2011 mass Shi'ite-led demonstrations demanding reforms in the Sunni-ruled Persian Gulf kingdom that were inspired by other pro-democracy uprisings of the Arab Spring.
If convicted, Rajab, founder of the Bahrain Centre for Human Rights, could find himself back in prison just months after completing a two years sentence in May for organising and participating in illegal protests.
Fellow activists who have maintained his official twitter account during past detentions confirmed the trial date.
In its statement, the Public Prosecution said the individual had "posted on his personal social media account insults against the two ministries in which he made defamatory allegations".
Rajab was detained for questioning shortly after returning to Bahrain from a trip abroad.
Bahrain, where the U.S. Navy's Fifth Fleet is based, crack down the protests but has since struggled to resolve political deadlock between the government and the opposition.
Many Shi'ites complain of political and economic discrimination, a charge the authorities deny.
Rajab was sentenced to three months in jail last year in a separate case over a tweet criticising the prime minister, the king's uncle. The ruling was overturned, but only after Rajab had already served his sentence.