Through the Employment Tribunal, Mendy has claimed 'unauthorised deductions from wages' after being found not guilty on charges of rape and sexual assault in 2021.
After the charges were made, the club suspended the former City star without pay. He last played for them in August 2021.
His contract expired at the end of June 2023 and he subsequently signed for French club Lorient.
In July, Mendy was found not guilty by a jury in a retrial at Chester Crown Court after being charged with rape and sexual assault.
The left-back, who has always denied the allegations, was accused of raping a 24-year-old woman in a bedroom in his Cheshire mansion.
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He was also charged with attempted rape of a 29-year-old woman from two years before.
According to Sky Sports, Mendy has now opened a 'multi-million-pound claim' against City for wages owed.
As such, he will now seek the salary owed to him from September 2021 up until the expiration of his contract in June 2023.
Sky Sports read a statement on behalf of Nick De Marco KC, the prominent sports lawyer acting on Mendy's behalf, which read: "Nick De Marco KC (instructed by Laffer Abogados (Madrid) is acting for the former Manchester City player Benjamin Mendy in a multi-million-pound claim for unauthorised deductions from wages.
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"Manchester City FC failed to pay Mr Mendy any wages at all from September 2021, following Mr Mendy being charged with various offences, all of which he was subsequently acquitted of, until the end of his contract in June 2023.
"The claim will come before an Employment Tribunal."
Sky Sports adds that Manchester City declined to respond when approached for comment.
Mendy signed for City in 2017 from Monaco in a £52million deal, making him the Premier League's most expensive defender at the time.
While at the Etihad Stadium, he lifted three Premier League titles and was part of France's World Cup-winning squad in 2018.
Mendy now plays for Lorient in Ligue 1, where he has made three appearances.