The South Korean outfit confirmed the promising star has completed terms to join Steve Bruce's side on a three-year deal at the Stadium of Light.
'Ji Dong-won is joining Sunderland on a three-year contract,' read a statement on Chunnam's official website.
Rising star: Sunderland have seen off rival competition to land highly-rated South Korea striker Ji Dong-Won (R)
'The terms negotiated by the two clubs regarding transfer fee and salary will not be released publicly.'
The 20-year-old international came to prominence at January's Asian Cup in which he scored four goals.
According to reports in Seoul, the fee is will likely be around ?2.1million for the forward who scored 11 goals in 39 appearances for Chunnam since making his professional debut in 2010.
Big challenge: Ji Dong-Won is looking forward to playing in the Barclays Premier League
'I had the impression that Sunderland really wanted me,' Ji told Yonhap.
'I know there will be stiff competition for playing time, and my goal is to become the player that the team wants me to be in six months.
'I am also looking forward to playing against (Park) Ji-sung and (Lee) Chung-yong, whom I both admire.'
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Explore more:People: Steve Bruce Places: Seoul, South Korea