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The right-back spent a season on loan at Parkhead from Stoke City, but did not play much as he was second choice to Jeremie Frimpong.
He still contributed to Neil Lennon's side winning a ninth title in a row.
He went on to play for Russian side Ufa and Swiss club Servette, leaving the latter in 2023 and not playing since.
Swiss sixth-tier side SC Veltheim, where Bauer began his youth career, have now confirmed his return.
A club statement said: "Moritz Bauer is returning to SC Veltheim.
"To the place where he once took his first steps as a footballer.
"In between lie over 15 appearances in the Premier League, games at the legendary Old Trafford, appearances for the Austrian national team, as well as the Scottish championship and cup victory with Celtic.
"A career that every little boy in Flüeli has probably dreamed of at some point."
The club also lauded his experience, saying: "With Moritz, we're gaining an incredibly down-to-earth, modest, and approachable person whose experience and personality are a great asset to our club.
"Someone who, despite his impressive career, has never forgotten his roots."
However, they tempered excitement with caution regarding his playing future: "After his hip surgery, Moritz's primary focus is on recovery.
"Whether and when he can return to the pitch remains to be seen.
"We certainly hope that he'll be able to enjoy a few minutes in the blue and white jersey again someday.
"Without pressure, without expectations, and without any promises.
"Because Moritz doesn't have to prove anything to anyone here anymore.
"His story speaks for itself."