Egypt tries prominent activist, Hossam Baghat, for critical elections tweet
Bahgat, director of the Egyptian Initiative for Personal Rights (EIPR), is already banned from travelling and his assets have been frozen due to another case in which he remains indicted.
Authorities have in recent years particularly targeted the group he founded.
Three EIPR staff members were jailed last year, sparking an international campaign supported by celebrities including Scarlett Johansson that resulted in their release.
Another EIPR researcher, Patrick Zaki, remains in detention since February 2020 facing charges of "spreading false news" after he returned to Egypt for a visit from Italy, where he was studying at Bologna University.
In July, the US State Department condemned Cairo for specifically indicting Bahgat saying dissidents "should not be targeted for expressing their views peacefully".
Bahgat is accused of "insulting" Egypt's electoral commission after he alleged that incidents of electoral fraud and vote rigging took place during last year's parliamentary elections.
Parliament is mostly comprised of loyalists of President Abdel Fattah al-Sisi and is viewed by critics as a "rubber-stamp" body.
Bahgat is also being prosecuted for "spreading false news", which can carry hefty fines and jail time.
"We will present evidence to the court of reports and information published by people involved in the elections," to support his allegations, Hoda Nasralla, one of Baghat's lawyers, told AFP.
Tuesday's hearing is the first and a verdict is not expected to come immediately.
Sisi, a former army chief, took power in 2014 and has launched a sweeping crackdown on dissent, with rights groups estimating that Egypt holds about 60,000 political prisoners.
Former US president Donald Trump forged a particularly strong relationship with Sisi.
His successor, President Joe Biden, vowed on the campaign trail that there would be no more "blank checks" for Egypt's president.
But Secretary of State Antony Blinken in May visited and praised Sisi for helping bring a truce that halted bloodshed in the besieged Gaza Strip when Israeli air strikes and artillery fire on the besieged enclave killed 253 Palestinians, including 66 children, and wounded more than 1,900 people in 11 days of conflict.