Santa Claus? Who is he?

He is just a fictitious character.

If you are more religious than most then you would think yes, because he was actually declared as a Saint (Saint Nick) because of the miracle of delivering presents to good little boys and girls throughout the world that believe in him. But if you're a skeptic then most likely no, because as you grow older you come to realize that it is none other than your parents placing those presents under the tree (it was my mothers handwriting that did it in for me) but deep down it is a sense that it was like a childhood memory that even adults still cherish and present to their children’s minds and hearts to help build their imagination and let them believe in something because as they grow older they tend to lose their sense of child like innocence and it's a way of holding on… that and make it to where they behave for at least a month. But yes as someone else said it, "Santa Claus is as real as one wishes him to be".