Captain Vincent Kompany says he will leave Manchester City after Saturday's FA Cup final win over Watford.
The 33-year-old defender won four Premier League titles, two FA Cups and four League Cups during 11 years at Etihad Stadium in which he scored 20 goals in 360 games.
By beating Watford 6-0 at Wembley, City became the first men's side to complete the domestic treble in England.
In an open letter on Facebook, Kompany said it "doesn't feel real".
"Countless of times have I imagined this day," he said. "After all, the end has felt nearby for so many years.
"Man City has given me everything. I've tried to give back as much as I possibly could."
Belgium centre-back Kompany joined City from Hamburg as a defensive midfielder in 2008 and was named club captain three years later.
He scored his final goal against Leicester on 6 May, a brilliant strike from 25 yards that was voted as goal of the season on BBC Match of the Day and took City to within one win of the Premier League title, which they sealed on the final day of the season with victory at Brighton.
"The time has come for me to go now," Kompany said.
"As overwhelming as it is, I feel nothing but gratefulness. I am grateful to all those who supported me on a special journey, at a very special club.
"I remember the first day, as clear as I see the last. I remember the boundless kindness I received from the people of Manchester.
"I will never forget how all Man City supporters remained loyal to me in good times and especially bad times. Against the odds, you have always backed me and inspired me to never give up."
City chairman Khaldoon Al Mubarak said: "There have been many important contributors to Manchester City's renaissance, but arguably none are more important than Vincent Kompany.
"He defines the essence of the club. For a decade he has been the lifeblood, the soul, and beating heart of a supremely talented squad.
"A booming voice in the dressing room yet a quiet and measured ambassador off it, Vincent can be as proud of himself as we are of him."