<p>In this paper, the design and simulation of a hybrid control structure using a fuzzy sliding mode controller (FSMC) and PID regulators for a six-DOF coaxial octorotor unmanned aerial vehicle (UAV) are presented. The dynamic model of the coaxial octorotor is derived using the Newton–Euler formalism and decomposed into four control subsystems: altitude, pitch, roll, and yaw. PID controllers are used in the translational x and y position loops to generate desired pitch and roll references, while the FSMC regulates the four main attitude and altitude subsystems. The proposed FSMC integrates fuzzy logic with the sliding mode framework to eliminate the chattering phenomenon while maintaining robustness against model uncertainties and external disturbances. To establish a rigorous proof of concept, this study is focused on a high-fidelity simulation environment. MATLAB/Simulink simulations under these controlled conditions demonstrate the superior accuracy, stability, and disturbance rejection capability of the FSMC compared to conventional methods in both nominal and perturbed flight scenarios. It is important to note that the present work serves as a foundational theoretical and numerical validation; practical implementation factors such as actuator saturation, sensor noise, and real-time computational constraints, while critical for final deployment, are reserved for subsequent experimental and hardware-in-the-loop studies.</p>