South Korea's Constitutional Court has removed President Park Geun-hye from office over a graft scandal involving the country's conglomerates at a time of rising tensions with North Korea and China.
The ruling sparked protests from hundreds of Park's supporters, two of whom were killed in clashes with police outside the court, and a festive rally by those who had demanded her ouster who celebrated justice being served.
"We did it. We the citizens, the sovereign of this country, opened a new chapter in history," Lee Tae-ho, the leader of a movement to oust Park told a large gathering in Seoul on Friday.
Park becomes South Korea's first democratically elected leader to be forced from office, capping months of paralysis and turmoil over the corruption scandal that also landed the head of the Samsung conglomerate in detention and on trial.
A snap presidential election will be held within 60 days.
Park was stripped of her powers after parliament voted to impeach her but has remained in the president's official compound.
The court's acting chief judge, Lee Jung-mi, said Park had violated the constitution and law "throughout her term," and despite the objections of parliament and the media, she had concealed the truth and cracked down on critics.
The ruling to uphold parliament's December 9 vote to impeach her marks a dramatic fall from grace of South Korea's first woman president and daughter of Cold War military dictator Park Chung-hee. Both her parents were assassinated.
Park, 65, no longer has immunity and could now face criminal charges over bribery, extortion and abuse of power in connection with allegations of conspiring with her friend, Choi Soon-sil.
Prime Minister Hwang Kyo-ahn was appointed acting president and will remain in that post until the election.
"It is time to accept, and close the conflict and confrontation we have suffered," Hwang said in a televised speech.
A liberal presidential candidate, Moon Jae-in, is leading in opinion polls to succeed Park, with 32 per cent support in one poll released on Friday. Hwang, who has not said whether he will seek the presidency, leads among conservatives, none of whom has more than single-digit poll ratings.
Park was accused of colluding with her friend Choi and a former presidential aide, both of whom have been on trial, to pressure big businesses to donate to two foundations set up to back her policy initiatives.
The court said Park had "completely hidden the fact of (Choi's) interference with state affairs."
Park was also accused of soliciting bribes from the head of the Samsung Group for government favours, including backing a merger of two Samsung affiliates in 2015 that was seen as supporting family succession and control over the country's largest "chaebol," or conglomerate.
Samsung Group leader Jay Y. Lee has been accused of bribery and embezzlement in connection with the scandal and is in detention. His trial began on Thursday.
On Friday, hundreds of Park's supporters, many of them elderly, tried to break through police barricades at the courthouse. Police said one 72-year-old man was taken to hospital with a head injury and died. The circumstances of the second death were being investigated.