"I'm sure that all City fans will play their part in driving us forward this year. It has been my dream to play my part in taking my hometown club to the Premier League, which would be fantastic for the football club, the city of Cardiff and Wales."
Cardiff boss Dave Jones said: "Bringing Craig to Cardiff is another big step in the development of this football club and I am delighted that he has agreed to join us on a season-long loan.
"Like recent additions Jason Koumas and Seyi Olofinjana, Craig is a great talent and adds to the quality players that we have here.
"We will continue to work on taking the next steps as a club and hope that all Cardiff City supporters join us in welcoming Craig by turning up in high numbers this season."
Bellamy, whose colourful career has taken in eight clubs already and cost nearly £45m in transfer fees, had earlier been given permission to train with Cardiff by Mancini.
The player had already been told he would be left out of City's 25-man Premier League squad due to be finalised by 1 September and had also been linked with moves to Tottenham, Fulham, Celtic, Everton.
Manchester City will be happy he has moved to the Championship rather than a Premier League rival.
Bellamy himself was so exasperated with his situation at Eastlands that he even spoke last week of quitting football altogether.
"This game is ruthless; I might finish, full stop," he stated at a Wales press conference.
Bellamy has been a Premier League regular since joining Coventry from Norwich in 2000 - except for a five-month loan stint at Celtic during his time at Newcastle United - and has also played for Liverpool, West Ham and Blackburn Rovers.
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