A woman's frantic search for her pet cat named Bear has come to a tragic end after its decapitated head was found in a neighbour's back yard.

A woman made the grisly discovery in the backyard of her Wynn Vale home in Adelaide's north-east and took to social media to help locate the cat's owner.

South Australia Police say there is a possibility the incident is connected to a recent arson attack, as the same woman's back fence was set on fire.

A woman's frantic search for her pet cat named Bear (pictured) has come to a tragic end after its decapitated head was found in a neighbouring back yard

The cat's owner was initially unaware her cat had been attacked and posted a message on Facebook in the hopes someone would return him.

However, she was devastated to learn the fate of her cat when she saw a Facebook post from the woman who discovered the animal's head.

An inspector from the RSPCA managed to identify the cat as the same long-haired, ginger and white cat called Bear.

The RSPCA says the way the head had been severed from the body indicated the decapitation was not an accident.

The cat's body is yet to be found.

Bear's owner said he would never wander far from his Para Hills home and had only been missing three days when she made the grim discovery.

RSPCA South Australia Chief Inspector Andrea Lewis said this case was particularly distressing.

'This cat was someone's much loved pet and one can only imagine the anguish his owner is experiencing as a result of this awful discovery,' Ms Lewis said.

Anyone with information about the incident is urged to contact the RSPCA.