The Sky Blues broken the British transfer record by paying £100m for the England playmaker.
Grealish, 25, will wear the number 10 shirt vacated by Sergio Aguero.
"I am incredibly happy to have joined Manchester City, City are the best team in the country with a manager considered to be the best in the world – it's a dream come true to be part of this club," Grealish said.
"Over the past 10 seasons, they have won major trophies consistently. Pep coming here has taken them to the next level and the football this team plays is the most exciting in Europe.
"To play for Pep and learn from him is going to be special and it's something any top footballer would want. "he facilities are amazing, and I honestly can't wait to get started, meet everyone and get playing."
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