Choi Seong-geum is a major character in Dae Jang Geum. She is considered the most notorious woman in the series, and is known as Lady Choi throughout much of the series. It is Lady Choi who killed Park Myeong-yi, her good friend, successfully plotted to oust Lady Han and Jang Geum from the palace, kicked Lady Min, Chang-ee, and Yeon-saeng out of the Royal Kitchen, attempted many times to get Jang Geum kicked out of the palace, and exploited the usually honest physician lady Park Yeol-ee. Lady Choi also goes against Lady Jung and Lady Han many times, trying to overthrow them. Despite her evil actions, however, Lady Choi cares only about her family, especially her niece Choi Geum-young. She teaches Geum-young that she must strive to raise her family to new heights so that generations later her ancestors' hard work does not become waste.
She dies in episode 48 from falling off a cliff on Mount Tongyin.
Choi Seong-geum was a real person in Korean history. However, the historical Lady Choi is worse than portrayed in the series. She allegedly forced Geum-Young to be one of the King's concubines.
The role of Choi Seong-geum was played by the Korean actress Kyeon Mi-ri.