Dr. Dre 'I'M THE 1ST BILLIONAIRE IN HIP HOP' ... Now Let's Celebrate!

5/9/2014 5:59 AM PDT

Dr. Dre -- 'I'M THE 1ST BILLIONAIRE IN HIP HOP' ... Now, Lets Celebrate!!

Ain't nuthin' like a BILLIONAIRE thing, baaaby ... just ask Dr. Dre who celebrated his MASSSIVE headphones deal with Apple last night by poppin' bottles and declaring himself the RICHEST MAN IN HIP HOP!!!!

After word broke that Apple was close to finalizing a deal to buy Beats for $3.2 billion, Dre went to the studio with Tyrese, F. Gary Gray (big-time movie director)  and some friends and got turnt all the way up with lots of champagne, Heineken and Hennessy. 

At one point, Dre looked into the camera and said -- "The first billionaire in hip hop ... right here from, the mother f**king West Coast!!"

Tyrese added, "Oh s**t, the Forbes list just changed!"

Sources at the studio tell us the gang partied until 4 AM. 

Unfortunately for Dre ... he can't buy his way out of a hangover -- but having a BILLION DOLLARS sure makes you feel better when you wake up.