Résumé : The robust estimation of discrete-time one-sided Lipschitz systems is considered. A linear matrix inequality based approach is presented to design a nonlinear state observer such that the input-to-state stability of the estimation error is locally guaranteed while minimizing an upper-bound on the ℓ∞-induced system norm from the disturbance input to the error system performance output. The effectiveness of the approach is demonstrated in simulation for several numerical examples.