The 25-year-old pugilist filed the lawsuit against his nemesis in New York on Friday ... alleging Garcia committed battery and fraud in the leadup to -- and during -- their big April 20 tilt at Barclays Center.

You'll recall, Garcia won the fight after knocking down Haney multiple times ... but the outcome was later ruled a no-contest after officials said Garcia had Ostarine in his system.

Haney said if he had known Garcia had ingested the performance-enhancing drug prior to stepping into the ring ... he wouldn't have agreed to the fight. Therefore, he says he never consented to being on the wrong end of Garcia's punches.

He also said, among other things, that by ingesting the banned substance despite agreeing to fight clean, Garcia made misrepresentations that would have caused Haney to back out of the matchup as well.

In addition to Garcia, Haney is also suing Golden Boy Promotions for breach of contract.

In his suit, Haney is suing for damages, claiming the entire ordeal caused him "physical injury, reputational damage which will amount to millions of dollars, and emotional and mental distress."