Milat had been serving a life sentence for killing seven backpackers between 1989 and 1992 and dumping their bodies in a New South Wales forest.
He died of cancer in a Sydney hospital early on Sunday local time.
Police said Milat's lifelong refusal to admit his crimes had hampered further investigations into the killings and other unsolved cases.
His murder victims were three Germans, two Britons and two Australians. All were aged between 19 and 22.
