An essential control objective of wind energy conversion systems (WECSs) is to maximize the conversion of wind energy into electrical energy. This control objective is difficult to achieve using linear control techniques because the WECSs are time-varying and highly nonlinear. In this paper, we propose a nonlinear fuzzy adaptive output feedback control strategy to achieve the optimum wind power extraction of the WECSs. The control strategy is based on the input-output feedback linearization and fuzzy approximation of controller synthesized to take care of the nonlinear, time-varying plant parameter changes. Numerical simulation results verify the superiority of the proposed control strategy in comparison with the nonlinear feedback linearization strategy.