Jose Canseco's ex-GF tells TMZ ... she believes J.C. is COMPLETELY INNOCENT ... and claims the woman accusing the former MLB star of rape is nothing more than a lying publicity whore.
We spoke to Leila Knight -- who dated Canseco for more than 4 years -- and she tells us she's spoken with Canseco at length about the sexual assault accusations that have been made against him in Las Vegas.
"I've been talking to him all day ... it's obvious that it's a publicity stunt, I mean -- the girl's an aspiring actress," Knight says.
Knight also says Canseco is a "gentle person" who always tells the truth -- "If anything, he's too honest."
For his part, Canseco has denied any wrongdoing ... despite the fact he's named as a suspect in a sexual assault investigation stemming from an alleged incident on May 10.