The authors propose a matrix model that exhibits manifest ten-dimensional \(N = 2\) super Poincaré invariance. They analyze interactions between BPS-saturated states and show that the massless spectrum matches that of type IIB string theory. The large-N reduced model of ten-dimensional super Yang-Mills theory is conjectured to be equivalent to this matrix model, suggesting a constructive definition of superstring theory. The paper includes detailed calculations of one-loop effective actions and renormalization, demonstrating the equivalence to string theory. The matrix model is interpreted as a classical limit of the reduced model, and the parameters \(\alpha\) and \(\beta\) are determined in terms of physical quantities. The double scaling limit and the generation of a chemical potential term are discussed, leading to the conclusion that the matrix model is a nonperturbative definition of superstring theory.The authors propose a matrix model that exhibits manifest ten-dimensional \(N = 2\) super Poincaré invariance. They analyze interactions between BPS-saturated states and show that the massless spectrum matches that of type IIB string theory. The large-N reduced model of ten-dimensional super Yang-Mills theory is conjectured to be equivalent to this matrix model, suggesting a constructive definition of superstring theory. The paper includes detailed calculations of one-loop effective actions and renormalization, demonstrating the equivalence to string theory. The matrix model is interpreted as a classical limit of the reduced model, and the parameters \(\alpha\) and \(\beta\) are determined in terms of physical quantities. The double scaling limit and the generation of a chemical potential term are discussed, leading to the conclusion that the matrix model is a nonperturbative definition of superstring theory.