Charles Manson -- the man who masterminded one of the most heinous murder sprees in American history -- is dead ... this according to the sister of his famous victim.
Debra Tate tells TMZ she received a call from the prison telling her Manson died 8:13 PM Sunday.
We're told the prison is contacting all of the victims' families.
Manson was recently wheeled into Bakersfield hospital and escorted by 5 uniformed cops. Our sources had said at the time, "It's just a matter of time." He was covered in blankets and looked ashen in the gurney.