We define a new category of quantum polynomial functors extending the quantum polynomials introduced by Hong and Yacobi. We show that our category has many properties of the category of Hong and Yacobi and is the natural setting in which one can define composition of quantum polynomial functors. Throughout the paper we highlight several key differences between the theory of classical and quantum polynomial functors.Proposition 2.2. The following diagram commutes:from which the commutativity of the diagram follows. Let (V, R V ) and (W, R W ) be Yang-Baxter spaces. We define the generalized (q-)Schur algebra S(V, W ; d) := (A(W, V ) d ) * as in [HY17]. The following is proved in [HY17]: Proposition 2.3. Let V, W be Yang-Baxter spaces. Then there is a natural isomorphism S(V, W ; d) ∼ = Hom B d (V ⊗d , W ⊗d ) Proof. See Proposition 2.7 in [HY17].By taking the dual of ∆ V,W,U we obtain a mapThere is a natural map m ′ U,W,V :The following Proposition shows they are the same map under the isomorphism in Proposition 2.3.Proposition 2.4. Given three Yang-Baxter spaces V, U, W , the following diagram commutes:Remark 2.5. If W = V , the quadratic relation (4) becomes the RTT relation due to Faddeev, Reshetikhin and Taktajan. The algebra A(V, V ) is then just the algebra denoted by A R V in [FRT88].