The 20-year-old Denmark international striker has signed a five-year deal.
The young striker who rose to prominence by notching 18 goals in Copenhagen's title-winning campaign, is expected to lead the Welsh side to Premier League safety.
Cornelius, who is 6ft 4in, has seven senior caps to his name already and has drawn comparisons to Denmark legend Jon Dahl Tomasson - and he is considered a better player than Arsenal striker Nicklas Bendtner was at his age.
The 2012/13 season was his first one for the Copenhagen, but the targetman became integral to club's plans after a series of impressive displays. He played a crucial role in their Super Liga win and was one of the consistent contributors, even winning a player of the month award in the process.
Copenhagen are getting good money to part ways with his services, while the Cardiff faithful are expecting him to blossom into an even better football with age on his side.
The youngster is unproven outside his country, but still the targetman is expected to cope with the demands of playing abroad. Cornelius might not be expected to hit the ground running immediately, as he is seen as a long-term investment in Malky Mackay's vision.
Cornelius had dreamed of playing in the Premier League and he is excited that his dream has come true at such a young age. He is impressed with the club's plans and their fan base and excited to play in Premier League.
With a manager like Malkay and players like Craig Bellamy to guide him, Cornelius seems to have chosen the right club to develop his career.
Cardiff fans will be eager to witness the new sensation at the Cardiff City Stadium - and he is expected to become a future star to carry the Welsh team's hopes.
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