Park Geun-hye, the first woman to be elected as President of South Korea was declared guilty of multiple counts of abuse of power, bribery, and coercion by Seoul Central District Court.
Park, 66, who the became the country's first female head of state in 2013, was convicted of bribery, abuse of power, and coercion.
She was indicted for corruption and other charges in April past year.
But on Friday the ruling was greeted with dismay in streets outside the courtroom by several hundred flag-waving Park supporters.
Many protesters sat or lay in the road crying, while others formed a protest rally calling for her release.
"The defendant abused the presidential authority delegated from the people of this country and it resulted in a large amount of chaos in terms of public order and state management".
The leader was, however, conspicuous by her absence at the court since she boycotted the trial accusing to be biased against her.
Instead she was informed of her fate at a Seoul detention centre, where she sat in a reception hall with her lawyer awaiting the outcome, Yonhap news agency reported. She is expected to appeal her sentence.
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Judge Kim Se-yoon said he had passed a tough sentence to "prevent such an unfortunate event from happening again". "We have to remember the past lest it repeats itself".
"What happened today is a sad thing for the country and for one person's life", Blue House spokesman Kim Eui-kyeom said in a statement.
Park acknowledges her ties with Choi in a nationally televised speech, but denies breaking the law.
Park was removed from office previous year following months of massive rallies that saw millions take to the streets calling for her to be ousted. Park has continued to say she is innocent of any wrongdoing.
Choi's sinister influence on Park was reportedly one of the reasons he was assassinated. He was sentenced to 2.5 years in prison.
The Seoul court convicted Park of colluding with long-time confidante Choi Soon-sil to pressure 18 business groups to donate a total of 77.4 billion won (£52 million) for the launch of two foundations controlled by Choi.
Park's corruption scandals were nothing short of apocalyptic for South Korea's political culture, looping in the giant electronics corporation Samsung and sending the billionaire heir apparent to the company, Lee Jae-yong, to jail for 12 years in December.
Her predecessor, Lee Myung-bak, was arrested last month on a raft of corruption allegations, including bribery, embezzlement and tax evasion.
Park once described Choi as someone who helped her when she had difficulties.