Tupac's Mom -- 'ECSTATIC' About New Musical

A new Broadway musical about Tupac Shakur just overcame one MASSIVE roadblock -- TMZ has learned, producers have obtained the approval of the rapper's notoriously protective mother ... who LOVES the show.

A rep for the Shakur family tells TMZ, producers personally gave Afeni Shakur a rough preview of "Holler If You Hear Me" -- the new musical by black theater legend Kenny Leon, based on Tupac's music.

According to the rep, Kenny wanted Afeni's approval before proceeding with the show -- and he GOT IT ... we're told Afeni was "ecstatic" and can't wait for the show to premiere.

The musical isn't about Tupac personally -- it's a fictional story about two childhood friends in a Midwestern industrial city and their extended families.