Rihanna loves to be nekkid … A LOT … but Instagram  says her displays of public nudity go way too far — and is now threatening the  singer within an inch of her exposed nipples.

Rihanna posted topless  snaps Tuesday from her photo shoot with Lui, a French skin mag — and  within an hour IG yanked ’em down … because they violated rules against  nudity.

Our Instagram sources tell us Rihanna got an email that basically  warned her … keep your clothes on or risk having your account permanently shut  down.

But like a bikini trying to contain her boobs — IG couldn’t stop  RiRi … and she just posted the banned nudes on Twitter instead.