Lawmakers in the National Assembly voted by a two-thirds majority on Friday to impeach Park Geun-hye as president over her alleged involvement in a corruption scandal that sparked public rallies across the country calling for her to step down.
The motion was adopted by a secret ballot with legislators voting 234-56 to oust the embattled president.
Following the vote, Park apologised to the people. She told a meeting of her ministers that she would prepare for a Constitutional Court review of the impeachment motion, a process that can take up to 180 days.
In the interim, Prime Minister Hwang Kyo-ahn will be acting president. She asked cabinet to work with the prime minister to avoid any vacuum in national security matters and the economy.
Parliamentary speaker Chung Se-Kyun announced the vote result:
"I declare that the bill to impeach President Park Geun-hye has just been approved," Chung said.
"Whether you support or oppose it, all lawmakers and South Korean people who are watching this grave situation unfold must feel so miserable and heavy at heart," he added.
"I deeply wish that such tragedy in our constitutional history will not be repeated ever again."
Park, 64, is accused of colluding with a friend and a former aide, both of whom have been indicted by prosecutors, to pressure big businesses to donate to two foundations set up to back her policy initiatives.
She has denied wrongdoing but apologised for carelessness in her ties with her friend, Choi Soon-sil.
Park, who is serving a single five-year term that was set to end in February 2018, said this week she would await the court's ruling, signalling that the political crisis could drag on.
Hours before the vote, anti-Park activists scuffled with police as they tried to drive two tractors up to parliament's main gate, where more than a 1,000 protesters were gathered.
Shane Hahm reports from Seoul.