The 25-year-old Togo international, who has penned a five-year contract, joins an impressive City forward line.
The big-spending Premier League club already boasts Carlos Tevez and Roque Santa Cruz, also signed in the close season, plus Robinho, Craig Bellamy and Benjani Mwaruwari.
"I have come here to make history for this club and those supporters. It's what the chairman and the manager told me they want too and I can't wait to get started," Adebayor told the City website.
City manager Mark Hughes added: "Emmanuel has been one of the top forwards in the Premier League since he arrived from France and we are delighted he has agreed to come and join us".
"His arrival is another clear indication that we are determined to augment the players we have here with the best of international talent."
He was cup-tied for Arsenal's 2006 Champions League final after playing in earlier rounds for Monaco.
"We'll miss him but, of course, we want to focus on the players who are with us at the moment and want to wish him well and thank him for what he has done for the club," Arsenal manager Arsene Wenger told Sky Sports.
"I'm sure he will give something special to Man City," he added just before the deal was announced.
Adebayor is City's fourth major signing of the transfer window following Tevez, who joined from Manchester United with a reported fee of 25.5 million pounds paid to his representatives, Santa Cruz who arrived from Blackburn Rovers and England midfielder Gareth Barry from Aston Villa.
"He adds vital balance and power to our attack," added Hughes. "He has everything a top forward needs. He is versatile, powerful, quick and agile on the ball.
"I am looking forward to working with him as are the rest of the staff. He will definitely add a new dimension to our play. I have been a great admirer for a long time."
