Eddie Murphy -- 'Purported African American' Sued For $50 MILLION ...

Eddie Murphy does NOT own the name Murphy ... and an indignant comedian -- Brando Murphy -- is determined to prove that point with a new $50 MILLION defamation lawsuit.

Brando claims Eddie is hell-bent on destroying his career, which Brando thinks is rooted in absurd vanity.

It looks like Brando is trying out new material in his lawsuit, saying, "The name Murphy is of Irish decent ... and not exclusive to Eddie Murphy, a 'Black Man' of African Ancestry and a purported African American."

As for Eddie's grumblings that Brando tries to look and act like him, Brando fires back, "[i] did not create [myself] and that the way [I] looks is an act of GOD."

Brando says he never tried to pass himself as Eddie's son. He does not address the fact that he appeared in the stage act, Sons of Comedy, which also featured Richard Pryor's son.

BTW ... Brando also claims one of Eddie's people threatened to have him killed.

For his troubles ... Brando wants a modest $50 mil.