Kevin Federline Sued -- You DESTROYED My Mansion ... and You're a Deadbeat!!

Kevin Federline is an inconsiderate homewrecker ... so says his former landlord ... who claims K-Fed trashed his L.A. mansion ... and then screwed him out of rent money.

Federleezy is being sued by Joseph Malek ... who claims Britney's ex moved in to his mansion in Tarzana, CA back in 2008 ... wrecked the place ... and then bolted without forking over a check for 7 months of rent.

Malek had threatened Federline with legal action back in 2009 ... claiming KFed turned the sprawling Valley property into a cigarette-riddled, spit-stained dump ... complete with broken smoke detectors and glass bottles littered all over the yard.

Malek had previously claimed KFed caused more than $110k in damage -- and now he wants a judge to force the former rapper to pay up.

Attempts to reach KFed were unsuccessful.