George Foreman says a woman accusing him of sexual abuse 45 years ago -- when she was a minor -- is intentionally dragging his name through the mud and flat-out lying ... so, now he's going after her in court.
Foreman filed his countersuit Monday against the accuser, Gwen H., who had initially sued the ex-boxer last summer. TMZ Sports broke the story ... she, and another woman, claimed Foreman groomed, and eventually sexually abused them, when they were still underage.