He will face questioning over his alleged acceptance of a luxury seaside apartment as a bribe from the OAS construction company.
The face to face meeting between Lula and Judge Sergio Moro in the southern city of Curitiba will be a highlight in the giant "Car Wash" graft investigation that has upended Brazilian politics, bringing down some of the country's most powerful men on both the left and right.
Lula, 71, became an icon of Latin America's left during a 2003-2010 presidency that saw Brazil enjoy a commodities-fueled boom and tens of millions of people lifted out of severe poverty. Today, he is fighting for his reputation -- and the chance of an epic comeback in elections next year.
The onetime shoeshine boy who became a union leader and founded the Workers' Party will face questioning Wednesday over his alleged acceptance of a luxury seaside apartment as a bribe from the OAS construction company.
The apartment and other alleged benefits from OAS are said to have been typical of a vast network of bribery in which major companies like OAS paid politicians to obtain influence with lawmakers and secure big deals with the Petrobras state oil company.
Already, senators, former ministers and the once seemingly untouchable speaker of the lower house of Congress, Eduardo Cunha, have been arrested or convicted, while scores more high-flying politicians face probes.
Lula denies any wrongdoing, saying there is no proof he had anything to do with the apartment. If he is found guilty when Moro hands down his verdict in an estimated 45 to 60 days, and then loses an appeal, he'd be barred from running for office again and face prison.
Despite his legal problems -- he faces five separate corruption court cases -- Lula remains hugely popular on the left and leads polls ahead of the 2018 elections. He also generates equally passionate hatred from opponents.
Moro, meanwhile, has become a hero to many for presiding over "Car Wash."
Wednesday's hearing is the first where the two protagonists will meet in person. However, Moro, 44, has already dueled repeatedly with the ex-president from a distance.
The first round was on March 4, 2016 when Lula was detained at his Sao Paulo house on a warrant issued by Moro and taken to a police station for questioning, before being released.
Soon after, then leftist president Dilma Rousseff tried to appoint Lula to her cabinet.
This would have taken him out of Moro's jurisdiction, but the move foundered when a wiretapped phone recording ordered by Moro was leaked to the media. The conversation apparently showed Rousseff and Lula discussing how getting him in the government would save him.
Meanwhile, Rousseff's own presidency was about to end, with impeachment proceedings gathering steam. In May, Rousseff was replaced by center-right President Michel Temer, meaning Lula had no friends left at the top table.
Moro struck his latest blow just this Friday, obtaining headline-grabbing testimony from former Petrobras director Renato Duque, who alleged that Lula "knew about everything" in the "Car Wash" conspiracy.
Lula supporters hope to bring as many as 30,000 people to demonstrate in Curitiba this week. There are also expectations that opponents will gather.
Fearful of violence, the authorities are pleading for people to stay away and are stepping up security.
"The idea is to make sure there is no contact between the two groups," said Curitiba security chief Wagner Mesquita.
On Saturday, Moro took the unusual step of issuing an appeal on Facebook.
"We want to avoid any kind of disturbance or confrontation. I don't want anyone hurt. Don't come, it's not necessary. Let justice take its course," he said.
Ever the fighter, Lula appears to be looking forward to his day in court.
"It's been two years that the media have been saying I'll end up in prison. Well, they should arrest me soon or otherwise it could be me having them arrested due to all their lies," he said Friday at a Workers' Party event.