Whitey Bulger -- one of America's most notorious mobsters -- was found dead Tuesday in a federal prison where he had just been transferred ... TMZ has confirmed
Bulger was just moved to a new facility -- U.S. Penitentiary Hazelton in West Virginia, a maximum-security prison. Prison officials haven't released details, but say his body was found sometime after he was moved to the prison.
Bulger had been serving out his life sentence in a federal pen in Florida until last week, when he was transferred to one in Oklahoma City ... and then recently arrived in Hazelton.