50 Cent Denies Claim That Fat Joe Tried to Assassinate Him

50 Cent's calling BS on the claim that Fat Joe wanted him dead back in the day ... showing love for his fellow New Yorker in a recent social media post.

The rapper took to Instagram to address claims made about Joe in a lawsuit earlier this week -- where the plaintiff Terrance Dixon accused him of allegedly offering a bounty on 50's life.

Dixon also alleged that Fat Joe ordered a hit to go down in NYC ... but, 50 was surrounded by "Navy Seal" type security -- so he was never attacked.

50's shutting down the rumor in its tracks ... writing on Instagram that the claims about FJ "are not credible."

He goes on, "I’m sorry joe has to endure the public scrutiny and damage to his reputation. THIS A STICK UP ! 🤨I wrote this hook I should a kept this one."

Joe responded with some appreciation for the support ... throwing a "100" emoji in the comments section.

Worth noting ... Dixon's claims about Fat Joe and 50 Cent are included in the same lawsuit -- filed by Dixon and his attorney Tyrone A. Blackburn -- we told you about earlier this week, where he was accused of having sex with underage girls.

Fat Joe's attorney, the A$AP-winning Joe Tacopina, told us ... the lawsuit is a blatant act of retaliation for a civil suit Fat Joe filed against Dixon.

Tacopina adds the accusations are "lies intended to damage his reputation and force a settlement through public pressure" -- and, law enforcement is aware of alleged extortionate demands Tacopina says Dixon has made of Fat Joe.