Who knew The Situation loves kitties THAT much? Um, yeah.

The Jersey Shore hunk is striking a shirtless pose in a new PETA campaign ad ... raising awareness for spaying and neutering cats.

Mike Sorrentino posted the above photo and the following, "It was a pleasure working with @peta on this campaign. A great cause with an important message! #support."

We all know Sitch loves to chase that tail!