Eminem Disses Snoop in New Song, 'Zeus' and Apologizes to Rihanna

Eminem's clapping back at Snoop Dogg in a new song after Snoop left him off his top 10 rappers list ... and he's also giving Rihanna a long-overdue apology.

The Detroit rapper just released a deluxe version of his album, "Music to Be Murdered By - Side B" and he responds to Snoop on his track, "Zeus."

Em raps ... "And as far as squashin' beef, I'm used to people knockin' me. But, just not in my camp. I'm diplomatic, 'cause I'm tryna be. Last thing I need is Snoop doggin' me. Man, dog, you was like a damn God to me. Man, not really. I had dog backwards."

Pretty soft as disses go, but Eminem's rebuttal comes after Snoop left him off his list of top 10 rappers of all time. Back in July, Snoop called Eminem "the great white hope" ... but basically Em owes all his success to Dr. Dre.

Em and Snoop have performed together -- they're both tight with Dre -- but now their beef seems to be heating up. It'll be interesting to see how/if they patch things up.

As for Rihanna ... Eminem said he's sorry for an older track -- not released, but leaked -- where he said he "sided" with Chris Brown.

He raps, also on Zeus, "But, me, long as I re-promise to be honest, and wholeheartedly, apologies, Rihanna. For that song that leaked, I'm sorry, Ri. It wasn't meant to cause you grief. Regardless, it was wrong of me."