Kelly Osbourne is jumping to the defense of her late father and his hometown … after WWE star Becky Lynch cracked a crass joke about him on “Monday Night RAW.”

Ozzy’s daughter went off on IG in response to Becky’s head-turning remarks … calling her a “disrespectful dirtbag.”

She continued unloading with … “Birmingham would not piss on you if you were on fire.”

ICYMI … Becky and Nikki Bella were in a heated confrontation in the ring ahead of their upcoming Intercontinental Championship match this Sunday.

Lynch told a crowd of Birmingham fans she wouldn’t do the match in their city … going on to say, “The only good thing that came outta here died a month ago” — which triggered a chorus of boos.

She doubled down on referring to the Prince of Darkness … adding, “But in fairness to Ozzy Osbourne, he had the good sense to move to L.A., a proper city. Because if I lived in Birmingham, I’d die too.”