<p>Active disturbance rejection control (ADRC) is recognized as a highly effective control strategy in the presence of uncertainties and disturbances, especially when a model is unavailable. It has been widely developed for various engineering applications. Although ADRC has been designed for both linear and nonlinear fractional-order systems, the synergetic technique has yet to be employed in designing ADRC for fractional-order systems. This paper introduces a fixed-time synergetic active disturbance rejection controller (FTSADRC) for nonlinear fractional-order systems, addressing stabilization and tracking under uncertainties and external disturbances. The approach begins with a fixed-time synergetic extended state observer (FTSESO) to estimate both system states and total disturbances. The fixed-time convergence of this observer is established. Based on these estimates, a fixed-time synergetic controller is designed to ensure stabilization and accurate tracking of reference trajectories, with robust compensation for disturbances. Closed-loop stability is analysed, and simulation results of the proposed FTSADRC, applied to fractional-order chaotic systems, are compared to those of the sliding mode active disturbance rejection control scheme.</p>