Monthe is said to have breached FA Rule E3 in the League Two game between Forest Green Rovers and Tranmere back in May. He 'vehemently denies' the allegation.
It is alleged the 26-year-old used 'abusive and/or insulting language' during the ninth minute of the game on May 1 that constitutes an 'aggravated breach'.
The language is said to have 'included a reference, whether express or implied, to sexual orientation'.
Walsall have issued a statement in response to the FA charge, which said: "We are aware of a charge made by the FA against defender Manny Monthe.
"The alleged incident took place during Manny’s time at Tranmere Rovers; prior to his arrival at the Banks’s Stadium in July 2021.
"Monthe vehemently denies the allegations and is looking forward to cooperating fully with the FA in order to clear his name as quickly as possible by following the correct process.
"The club or player will be making no further comment at this stage."
Monthe has until Thursday, October 21 to officially respond to the charge.