A grim-faced Park, wearing a blue trouser suit, a badge with her prisoner number, and no make-up, walked into the courtroom at Seoul Central District Court, avoiding meeting the glance of her longtime secret confidante and co-accused Choi Soon-Sil.
The trial, expected to last for months, is the final act in the drama that engulfed Park, the daughter of a dictator who went on to be elected president herself before she was sacked by the country's top court in March.
Presiding judge Kim Se-Yun asked her: "What is your occupation, the accused Park Geun-Hye?"
She responded: "I don't have any occupation."
The fallen head of state was brought to the building in handcuffs, transported from a detention centre in a justice ministry bus, with at least six guards on board.
Park, 65, was impeached by parliament following revelations of her involvement in a massive graft scandal centred on Choi, her friend of 40 years, and implicating some of the country's top businessmen.
Soon afterwards she was detained and indicted.
Tuesday's opening session was Park's first public appearance since she was taken into custody in March.
The trial could shed new light on the ties between Park and the bosses of the family-run conglomerates that dominate Asia's fourth-biggest economy and who allegedly bribed her.
They include Samsung heir Lee Jae-Yong, who is being tried separately, and Shin Dong-Bin, the chairman of retail giant Lotte, the South's fifth-biggest conglomerate, who was among the accused Tuesday.
Park faces 18 charges including bribery, coercion and abuse of power for offering governmental favours to tycoons who bribed Choi.
Choi, the daughter of a shadowy religious figure who was Park's mentor for years, is similarly accused of using her presidential ties to force top firms to "donate" nearly $70 million to non-profit foundations which she then used for personal gain.
Park is also accused of letting Choi, who has no title or security clearance, handle a wide range of state affairs including senior nominations and even her daily wardrobe choices.
'Chapter of history'
The proceedings took place under tight security, and hundreds of people flocked to the court to enter a lottery for seats in the public gallery.
"I am here to witness a new chapter of history being unfurled," spectator Lee Jae-Bong, 70, told AFP.
"I think Park must be punished thoroughly and never be pardoned so that such a bad thing may never happen again".
If convicted of the most serious charges, Park faces a minimum sentence of 10 years in jail, and a maximum of life.
The hearing comes only two weeks after the country elected left-leaning former human rights lawyer Moon Jae-In -- who lost the 2012 poll to Park -- as her successor.
Park Young-Soo, who led the special prosecutors who investigated the case, has said the proceedings will be "the trial of the century".
Park grew up in the presidential palace as the daughter of late dictator Park Chung-Hee, who ruled from 1961 until his assassination in 1979, and rose to power largely on the back of his continuing popularity among the aged voters who benefited from rapid economic growth under his tenure.
His mixed legacy of economic development and political repression has been a subject of heated debate for decades.
Park is the third former South Korean leader to stand trial for corruption following Chun Doo-Hwan and Roh Tae-Woo, who served jail terms in the 1990s for charges including bribery and treason.
In addition, ex-president Roh Moo-Hyun -- the mentor of new leader Moon Jae-In -- killed himself after being questioned over graft.
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