Mo'Nique filed the papers in Fulton County in response to her landlords' lawsuit -- which claims the actress bailed on her two-year lease agreement, signed in March, and owes $370,000 in unpaid rent and other charges.

But Mo says it's all crap ... literally ... insisting there's a damn good reason she's walking out on the rental contract -- the house stinks of dog feces, wet dog, and urine (of unknown origin) ... not to mention an overflowing septic tank.

But it doesn't end there -- according to Mo'Nique, the house also had a bad mold problem and the security gate was busted.

Mo'Nique claims she struck a verbal agreement with the landlords, allowing her to renege on her contract with 60 days notice because of all the problems -- but Mo' claims her landlords aren't living up to their word.