The approach to robust stabilization of linear systems using normalized left coprime factorizations with H ∞ bounded uncertainty is generalized to nonlinear systems. A nonlinear perturbation model is derived, based on the concept of a stable kernel representation of nonlinear systems. The robust stabilization problem is then translated into a non-linear disturbance feedforward H ∞ optimal control problem, whose solution depends on the solvability of a single Hamilton-Jacobi equation.