In mathematics, especially in the study of dynamical systems and differential equations, the stable manifold theorem is an important result about the structure of the set of orbits approaching a given hyperbolic fixed point.
Let
                    f        :        U        ⊂                              R                                n                          →                              R                                n                                  be a smooth map with hyperbolic fixed point at                     p                . We denote by                               W                      s                          (        p        )                 the stable set and by                               W                      u                          (        p        )                 the unstable set of                     p                .
The theorem states that
                              W                      s                          (        p        )                 is a smooth manifold and its tangent space has the same dimension as the stable space of the linearization of                     f                 at                     p                .                              W                      u                          (        p        )                 is a smooth manifold and its tangent space has the same dimension as the unstable space of the linearization of                     f                 at                     p                .Accordingly                               W                      s                          (        p        )                 is a stable manifold and                               W                      u                          (        p        )                 is an unstable manifold.