The purpose of this paper is to introduce a category whose objects are discrete dynamical systems (X, P, H, theta) in the sense of [6] and whose arrows will be defined starting from the notion of groupoid morphism given in [10]. We shall also construct a contravariant functor (X, P, H, theta) -> C* (X, P, H, theta) from the subcategory of discrete dynamical systems for which PP-1 is amenable to the category of C*-algebras, where C* (X, P, H, theta) is the C*-algebra associated to the groupoid G (X, P, H, theta).