The distressed animal was found leaning against a wall with a bleeding leg in the village of Hurlford, East Ayrshire.
An X-ray revealed that her front leg had been shattered by an airgun pellet and vets had no option but to amputate.
The SSPCA fear more animals could be targeted. It follows two incidents in the same village where animals died after being deliberately poisoned.
The injured cat, which staff have named Poppy, is now being cared for at SSPCA's Glasgow Animal Rescue Centre in Cardonald, while the charity try to trace her owner.
Alistair Hill, Animal Rescue Officer, said: "Poppy had been seen visiting gardens in Hurlford over the past 10 days or so and it seems that she has now been cruelly targeted in a malicious airgun attack.
"As well as appealing for any information on this incident we're also trying to trace this poor cat's owner.
"She's not micro-chipped, nor was she wearing a collar, so we're hoping someone out there will recognise her.
"This isn't the first time we've been called to investigate cat-related cruelty in Hurlford. In December 2008 we investigated two cat deaths as a result of carborfuran poisoning.Unfortunately the source was never found and the incidents ceased after we publicised the matter, but it now seems that cats are once again the subject of animal abuse.
"This is yet another disturbing example of a defenceless creature being maimed as a result of airgun misuse."
Anyone who recognises Poppy is being asked to call the SSPCA's Animal Helpline on 03000 999 999.
A charity, Missing Cats in Scotland, has launched a petition calling for airguns to be banned, which has been backed by around 350 people so far.
To sign the petition go to http://epetitions.direct.gov.uk/petitions/54791