Canan Kaftancioglu, a senior member of the Republican People's Party (CHP), has been accused by the prosecution of insulting the President, of spreading terrorist propaganda and inciting hatred over tweets she sent between 2012-2017, but particularly around the time of the 2013 Gezi protests.
The Gezi protests began on a small scale against the redevelopment of Taksim Gezi Park in central Istanbul but spiralled into a nationwide clamour against the government after the police responded with tear gas and water cannon against peaceful protesters.
At the time, Erdogan then serving as Prime Minister condemned the demonstrators as looters and vandals.
In one of the tweets, Kaftancioglu likened the Turkish state to a "serial killer" after 14-year-old Berkin Elvan was killed by a tear gas canister during the demonstrations.
At least 12 people were killed during the Gezi protests, 36 people lost their eyes and thousands were injured, reports say.
Hundreds of her supporters gathered at the court in Istanbul as the hearing got underway, Efe news reported.
Several Erdogan critics have faced charges of "insulting the President" since the leader of the Justice and Development Party (AKP) came to power five years ago, which has been condemned by Human Rights Watch.
In 2017, more than 2,000 people were found guilty of the charge and prosecutions of many more were ongoing in 2018.
The charges against Kaftancioglu also relate to posts she penned following the assassination of three Kurdish activists in Paris in 2013, in which she borrowed a term from one of the victims, co-founder of the outlawed Kurdistan Worker's Party (PKK) Sakine Cansiz: "The history of the mankind starts with a woman. Humanity loses due to things done to women."
Since she was elected to the chair of the CHP Istanbul branch, Kaftancioglu spearheaded a campaign to end the AKP's 25-year rule in the city, Turkey's largest.
As a female politician, Kaftancioglu found herself on the receiving end of slander from Islamist and nationalist politic and was attacked by AKP trolls on the social media immediately after she was elected CHP chair.
"Kaftancioglu is not alone", a civilian initiative in support of the politician, was organized after the court accepted her indictment earlier this year.
( With inputs from IANS )