Separately, 30-year-old Jung was convicted of filming himself having sex with other women without their knowledge and sharing the footage without their consent.
The sentence for Jung is two years less than what prosecutors demanded; the court agreed with the prosecution on Choi.
After a long court battle, Seoul Central District Court sentenced pop singer Jung Joon-young to prison for 6 years.
"We can't imagine the pain the victims might have felt who found out later".
Some think Jung and Choi, 29, who quit pop-rock band FT Island after he was implicated, could be suffering from a sexual disorder and will benefit from the rehabilitation programme.
Friday´s verdict came just days after the death of Goo Hara, a former member of girl group Kara, in an apparent suicide after she was blackmailed.
Jung - who retired from the entertainment industry in March admitting to part of the allegations - was also charged with filming the assault and distributing the footage in a chatroom through KakaoTalk, a messaging app.
The court said in a statement that they were convicted of committing "special quasi-raping", which it said means multiple people collaborating to have illicit sexual intercourse with a person who was unconscious or unable to resist.
Lawyers for Jung and Choi could not be reached for comment.
Both men must complete 80 hours of sexual violence treatment courses and are prohibited from working with children, the outlet reported.
"I deeply regret my foolishness and I feel great remorse".
The identities of the victims were suppressed to protect their privacy.
Prosecutors developed a case against Jung and Choi after Jung shared some of the videos in a group instant message that included Seungri, a member of the highly popular K-pop group Big Bang, which has sold over 140 million records worldwide.
But while the minimum sentence for rape in South Korea is three years most online commentators said the penalties were too lenient.
Officials investigating Seungri requested copies of his private communications, revealing the group text messages in which Jung shared his videos with other friends in the music industry.