The Eastlands outfit have landed the Italy striker on a five-year deal after agreeing an undisclosed fee with Inter thought to be around £24million.
City boss Roberto Mancini told the club's website: "I think that Mario is one of the best players of his age in Europe, and I very happy to be working with him again.
"His style of play will suit the Premier League, and because he is still so young there is a big chance for him to improve. He is a strong and exciting player, and City fans will enjoy watching him."
Balotelli admits he is leaving Inter with regret, but felt he had no choice following a difficult year.
"Soon I'll be starting on a new adventure," he wrote on his website. "I'm sorry that I'm leaving Inter and Italy because I would have preferred to continue my professional career in my own country.
"I'm going where I hope to find the space I need to play which is very important to me: I need to play, to make mistakes, to learn and to play again. As well as a calm environment around me.
"It's been a difficult year. I've recognised my mistakes, but I think I've often been under pressure and on the receiving end of criticism that at times has irritated me.
"Now all I'm thinking about is playing well for my new club and in the Premier League. I really want to give it my best try!
"I'd like to thank my family, who have supported me with so much patience and affection, through both the good times and the difficult periods.
"I also want to thank club chairman Moratti, the team I've shared so many victories with, the fans who've supported me, my entourage and my friends."