<p>This paper introduces a novel robust trajectory tracking control algorithm for a single-link flexible manipulator that uses a state observer-based integral sliding mode approach. The inherent flexibility present in the manipulator link introduces challenges in achieving precise trajectory tracking due to dynamic complexities and vibration at the tip. In order to overcome these difficulties, an integral sliding mode control law is designed that provides resilience against external disruptions and model uncertainties. A state observer complements the proposed control approach, ensuring the precise implementation of the proposed control algorithm with output measurement alone. The proposed control’s efficacy is established through numerical simulations and experimental verification.</p>