50 Cent, Floyd Mayweather Beef: Rapper's Viral Instagram Rant, 'Ray J's Hooking Up with Boxer's Girlfriend Princess!' [PHOTOS]

Rapper 50 Cent and undefeated professional boxer Floyd Mayweather, Jr. used to be great friends... but now they're simply great ENEMIES. Fifty and Mayweather have been involved in an ongoing feud for quite some time... and now, the Get Rich or Die Tryin' emcee's throwing fellow singer Ray J into the mix...

Check out this Instagram photo Fifty posted over the weekend:

50cent: "I GOT FLOYD, I GOT RAY J At the same damn Time."

The lovely lady in this pic is known as Princess... allegedly one of Mayweather's several "infamous" girlfriends. According to MediaTakeOut.com, Princess is Mayweather's third main squeeze... coming in after fiancee Shantel and baby mama Melissa.

And according to Fifty, she's also hooking up with Kim Kardashian's ex Ray J behind Mayweather's back.

50cent: "@Floydmayweather don't feel Stupid some of them belong on a TRACK that's all #smsaudio."

Woah.

Just when fans thought the beef between Fifty and Mayweather was simmering down... the G-Unit emcee fires things up again! What do readers think about Fifty's viral (and accusatory) Instagram post?