Chief Keef is swimming in cash but he's not handing any of it over to his landlord ... who claims the rap prodigy owes almost $10k in back rent.
Georghe Simoniak-Sas filed a lawsuit against Keef -- real name Keith Cozart -- and Keef's uncle. In docs, Georghe says Keef hasn't coughed up rent for the months of July or August ($4,700 /month) on the Illinois mansion he's renting ... but continues to live there.
Georghe says enough is enough ... he's suing for eviction and to collect $9,400 in back rent.
As for the digs ... 5,100 square feet, 6 bedrooms, 5.5 baths. Valued at over $1 million.
Which we're pretty sure Keef can afford.