Bradley Murdoch was convicted in 2005 of murdering Peter Falconio, 28, and assaulting his girlfriend Joanne Lees at gunpoint on a remote stretch of highway near Barrow Creek, about 200 miles north of Alice Springs in the Northern Territory, on July 14, 2001.
Murdoch is believed to have hidden Mr Falconio’s body, which has never been found despite extensive searches.
Northern Territory Police said in a statement that the missing person’s case remains open.
Detective senior sergeant Karl Day said: “Police are urging anyone out there, with any information that may assist Peter’s family in gaining some sort closure, to come forward and contact police.
“We are thinking of Peter’s family and friends on this anniversary and remain hopeful that such a milestone may jolt some information and progress the investigation.”
Ms Lees returned to the Outback for the first time in 15 years in February 2017 in the hope of finding the body.
The then 43-year-old, from Huddersfield, said she wanted to “bring him home” as she returned to the scene of the shooting for an Australian television show special.
She fought back tears as she added: “It’s because I love Pete so much and I want to bring him home and I need to bring him home.”