Grealish came through the Villa youth ranks and spent eight years with the first team, making 213 appearances and scoring 32 goals.
Man City matched Grealish’s release clause and confirmed his arrival at the Etihad Stadium on Thursday.
“I’ve been at Aston Villa for 19 years and I’ve been a fan my whole life. I’ve come up through the ranks and captained my club back to the top tier of English football. It’s impossible to put my feelings into words, but I’ll try,” the England international wrote in an open letter.
“When I first came to Villa I had my own personal dreams and ambitions like getting into the first team, scoring my first goal and scoring the winner in a derby. It wasn’t until we got relegated that I felt a greater sense of purpose.”
“Every time I put on the Villa shirt I played with my heart on my sleeve, being given the armband was both a privilege and an honour for me and my family and I’ve loved every minute of it.”
“I want to thank the manager and my teammates, I’ll never forget everything we achieved together… and to the fans who have supported me through everything, I can’t thank you enough.”
“All my coaches and all the people who work at the club behind the scenes who have done so much for me over the years – thank you.
“I’ll always be a Villa fan – I love this club with all my heart and I hope you understand my reasons for seeking a new challenge.
“The club are in great hands, the manager, the lads, the new signings coming in – it’s an exciting time to be a Villa fan.
“I’ll see you all again soon. Until next time. UTV, Jack.