Germany's Mueller to leave Bayern Munich after 25 years
The 35-year-old, whose contract was set to expire in the summer, said in a post on social media the decision was made by the club and "not what I would have wished".
Mueller said he did not like how the contract saga played out "back and forth in public" in recent months but he "felt the appreciation from everyone involved after my long time with Bayern".
"The special connection to the club and our fantastic fans will always remain," he said.
Mueller came through the Bayern junior system and has won two Champions Leagues along with 12 Bundesliga titles.
His focus was now on "bringing the league title back to Munich" as well as reaching this season's Champions League final, which will be held in Bayern's Allianz Arena home.
Later on Saturday, Bayern issued a statement saying Mueller would be honoured with a testimonial match and that the midfielder would play at the Club World Cup in July.
"Thomas Mueller had the definition of a Bavarian fairytale career," club president Herbert Hainer said.
Mueller was born in the nearby Bavarian town of Weilheim and joined the club aged 10, making his debut under coach Jurgen Klinsmann in 2008 against a Hamburg side featuring current Bayern coach Vincent Kompany.
A one-club player, Mueller's 743 matches for Bayern in all competitions is the most in the team's history. He has registered 247 goals and 273 assists for the club in that time.
In recent seasons, Mueller has started from the bench more regularly, leading to growing speculation he could leave the club.
The midfielder did not reveal where he would play next season, although German media has speculated he could make a late-career move to the United States to play in the MLS.
'Focus on the future'
Former teammate at Bayern Eric-Maxim Choupo Moting, who plays for the New York Red Bulls in the MLS, told Kicker that Mueller was "welcome here" in March.
"Thomas is a Bayern legend so I would be happy for him if he continues there. If he wants to take the step (to the US), we'll see.
"Thomas, you already speak English... I'm watching you."
Mueller has long been earmarked for a role in the club's administration once his playing career ends.
A 2014 World Cup winner with Germany, Mueller retired from international duty just after Euro 2024.
He played for his country 131 times over a 14-year period, scoring 45 goals.
Bayern sporting director Max Eberl said in a statement the decision not to continue with Mueller was "anything but easy," adding "we're putting the focus on the future".
Bayern's next match is Tuesday's home Champions League quarter-final first leg against Inter Milan, with the return game the following Wednesday.
An injury to Jamal Musiala in Friday's 3-1 win at Augsburg could mean Mueller is in line for a rare start against the Italian champions.
In the league, Bayern sit nine points clear of defending champions Bayer Leverkusen, who have a game in hand at lowly Heidenheim on Saturday.