The two stars have been going at each other ever since Eminem targeted MGK on Not Alike, a tune from his hit latest album Kamikaze.
Kelly responded with his own diss track, Rap Devil, and now the Lose Yourself hitmaker is firing back on his new release, which comes with artwork featuring his rap rival's face as the target of a gun with a smiley face bullseye on his forehead.
On Killshot, Eminem raps: "Younger me? No, you're the whack me/It's funny, but so true/I'd rather be 80 year old me than 20 year old you".
He also pokes fun at the younger rapper's look, adding: "How you gonna name yourself after a damn gun and have a man bun?".
Eminem also takes aim at critics, who have suggested Kelly is the new Eminem, insisting the two rappers don't belong in the same league.
"You ain't never made a list next to no Biggie, no Jay/Next to Taylor Swift, and that Iggy ho, you about to really blow".
"Killshot" was released digitally on Friday, September 14.