She first spoke out loud when the presiding judge asked what her occupation was.
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. They are friends of four decades but did not acknowledge each other.
In contrast, Choi was tearful when she addressed the court.
Park stared straight ahead as prosecutors read out the charges.
Park isn't the first South Korean president to face trial.
The courtroom was packed, with spectator Lee Jae-Bong, 70, telling AFP: "I am here to witness a new chapter of history being unfurled".
"Yes", Park replied, "I have the same position as the lawyers".
Park's court appearance is the first time she has been seen in public since her arrest in March.
March 10, 2017: Park is formally removed from office after the Constructional Court upholds her impeachment.
During a televised apology in October, Ms. Park described Ms. Choi as a close friend who "helped her during hard times in the past". Lee faces a separate trial. The former president appeared at an open court room with prisoner number 503 inscribed on her lapel.
She is expected join the former president in court on Tuesday, and judge Kim Se-yoon is expected to decide whether to try them together or to split the cases.
About 150 of her supporters gathered outside the court, weeping and screaming with outrage as Park's prison bus passed by. But she has spent the past weeks in a small cell with a mattress, table, sink, toilet and television.
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.
It is a stunning fall for a woman who won the 2012 presidential election over Moon by more than a million votes. Choi was present at the trial.
Choi has been on trial for months for her alleged role in the bribery and influence peddling scandal but also strongly denies the charges.
The court adjourned around midday, with the next trial day scheduled for Thursday, May 25.
Every president elected after the country's transition toward democracy in the late 1980s faced scandals near the end of their terms.
Park has denied any wrongdoing and pleaded not guilty at the trial and her lawyers rejected the 18 charges against her in pre-trial proceedings.
The trial, which is expected to last months, could see the spotlight turned on some big corporate and political names of the country. Lee paid the bribes in return for the government's backing of business deals, including a merger of two Samsung companies in 2015. Mr.
As for 22 billion won Park received from Samsung as contribution to Choi's Mir and K-Sports Foundations, the prosecution charged the former president with third-person bribery.
1963: Park moves to the presidential Blue House after her father becomes president, two years after he staged a coup and took control of the country.