Cats do have a belly button just like any other animal that is born with an umbilical cord. The belly button is where the umbilical cord connects an animal to its mother.
The belly button of a cat can be hard to find. As a kitten grows, its belly button decreases in size and becomes nearly impossible to see. When kittens are born, owners are sometimes tempted to remove the umbilical cord; however, for the cat's safety, this is not recommended.
When a female cat has been spayed, the resulting scar can be confused for the belly button. This has prompted many vets to use tattoo ink to mark the incision site.