Jay Z And Beyonce Have A BLOW UP FIGHT . . . Over Kim Kardashian!!! (. . . And Bey WALKS OUT On Jigga)

The fallout of introducing TRASH like Kim Kardashian into Kanye West's inner circle has begun. ImYourMedia.com EXCLUSIVELY learned that Jay Z and his wife BEYONCE are having what one insider calls as the "biggest fight of their marriage."

What happened? Well it has to do with the 40th BIRTHDAY PARTY of Jay Zs LONGTIME best friend TyTy. Jay and a number of friends had been planning for MONTHS to throw TyTy a huge 40th bash in London, England.

And everything was all set . . . until KIM KARDASHIAN came into the picture. You see, Kim asked Kanye West to TAKE HER to the event - which was to be attended by some of the BIGGEST CELEBRITIES IN THE WORLD - and Kanye agreed. That was a PROBLEM for Beyonce.

A snitch tells ImYourMedia.com, "Beyonce didn't want to go when she learned that Kim [Kardashian] would be there. She asked [Jay Z] to uninvite [Kim]. But [Jay] was like, 'That's Kanye's guest, and I can't uninvite her.'"

So Beyonce did the UNTHINKABLE . . . she REFUSED TO ATTEND. The ImYourMedia.com insider continued, "Jay was upset and hurt. That's his best friend in the world, TyTy [and his family] vacation with [Jay and Bey] . . . and he's the godfather to Blue. . . [Jay Z] thought it was disrespectful for [Beyonce] to not attend just because of [Kim]."

Now y'all KNOW that we usually ride with Beyonce. But we're with JIGGA on this one . . . But look at the MESS that Kim is causing already . . . SHEESH!