The first national gun amnesty since the Port Arthur massacre will aim to keep some of Australia's 260,000 illegal guns out of terrorists' hands.
The three month amnesty will allow people to hand in unregistered guns from July 1.
"This is an opportunity for people to present the guns to authorities, no questions asked and with no penalty," Justice Minister Michael Keenan said on Friday.
"If people don't take that opportunity, the penalties for owning an unregistered or illegal gun in Australia are very severe."
He says illegal guns were used in the Lindt Cafe siege and the death of police accountant Curtis Cheng in Sydney, as well as being used in organised crime.
"We have seen, through terror attacks in Australia, that illegal guns have been used," Mr Keenan said.
"Now is the time to run another amnesty, with the aim of reducing this pool of illegal guns."
Mr Keenan gave the example of a family heirloom that might have been sitting in a garage, and people might be worried about the consequences of handing it in.
"What we want to do is reduce the number of guns like that in the community," he said.
The national amnesty will be the first since the Port Arthur massacre in 1996, which was accompanied by a gun buyback scheme.
Mr Keenan said more recent state-based gun amnesties had seen thousands of illegal guns handed in.
Fellow cabinet minister Christopher Pyne says if illegal guns weren't available, they could not have been used in the recent killing of Queensland police officer Brett Forte.
Labor is backing the amnesty.
"We would certainly encourage people to do the right thing and to hand them in," frontbencher Anthony Albanese told the Nine Network.
The Port Arthur shooting in April 1996 resulted in the deaths of 35 people at the popular tourist site in Tasmania.
Gunman Martin Bryant is serving 35 life sentences for the murders.
