An RSPCA spokeswoman said the severe nature of the cat’s injuries meant his entire leg had to be amputated.
Investigators are now calling on the public to help locate the cat’s owner and to track down the origin of the illegal trap.
They said it was unclear how many days the cat had spent trying to free itself from the trap, or how far it had travelled.
The male black and white cat was wearing a blue collar with a bell but had no identification tags or microchip.
“This cat would have been in significant physical pain and experienced severe mental distress,” RSPCA inspector Kate Davies said.
“We are currently encouraging anyone who has seen something that may contribute to this investigation to come forward with information.
“This was a horrific act of animal cruelty and our thanks go to the person who found the animal and reacted quickly to prevent the cat from further suffering.”
Serrated steel jaw traps are illegal in Victoria. It is also illegal to set any leghold trap for the purpose of trapping domestic animals.
Ms Davies said those responsible for the cat’s injuries could face up to two years’ jail and fines of more than $80,000.
Residents in the Mooroolbark area in particular are being urged to report anyone who is known to own or set these traps or have traps, similar to the ones pictured, in their possession.
Anyone with information is encouraged to call 03 9224 222 or visit www.rspcavic.org/report
Erin covers crime for The Age. Most recently she was a police reporter at the Geelong Advertiser.