Park's ousting, the first for a democratically elected South Korean president, sparked angry scenes outside the courtroom with two of people killed in clashes with police, according to the local Yonhap news agency.
The court ruling rubber-stamps December's parliamentary impeachment of Park, who has been suspended from office pending the judges' decision.
An election for a new president needs to occur within the next 60 days, with the Prime Minister Hwang Kyo-ahn to continue in his temporary position of leading the country until they have taken place.
Park is accused of assisting Choi Soon-sil, a close friend of 40 years, of bribery and corruption. While Choi is already facing corruption charges, Park has so far had presidential immunity.
Today's decision paves the way for prosecutors to open against the now former president.
Both Park and Choi deny any wrongdoing.
Judges ruled eight to zero in favour of removing Park from office, concluding her actions had "seriously impaired the spirit of... democracy and the rule of law" and she had "concealed completely Choi's meddling in state affairs and denied it whenever suspicions over the act emerged and even criticised those who raised the suspicions."
Park did not appear at today's hearing and has refused to give evidence to investigators.
Today's decision was largely welcomed by the people of South Korea, although the angry scenes outside the court house led to the deaths, one of which was an elderly man who fell from a police van, local news channels reported.