<p>This paper investigates a prescribed performance anti-saturation fast super-twisting sliding mode control strategy based on a disturbance observer to address the attitude tracking problem of fixed-wing unmanned aerial vehicles. A fast finite-time disturbance observer is employed to estimate unknown lumped disturbances, and an auxiliary system is introduced to compensate for actuator saturation. To improve the transient and steady-state responses of the system, a tubular performance function with a narrow feasible domain is proposed that effectively suppresses overshoot and allows the setting of convergence time. Based on this performance function, a fast super-twisting sliding mode control algorithm is designed, which ensures the smooth, high-precision, and chatter-free tracking of the target attitude. Theoretical analysis confirms the fast finite-time convergence property of the system; comparative simulations validate the superiority of the proposed method.</p>