Fins play a vital role in improving the directional stability of aerial vehicles. However, airships are characterized by an inherent directional instability due to undersized fins. In this paper, a systematic approach to the design of airship fins is proposed. A constrained optimization problem is formulated to identify the optimal location, span, and chord of the airship fins. A semi-empirical aerodynamic model is used to formulate the objective function that represents the directional instability of an airship. The validity of the numerical solution acquired by minimizing the objective function with other design constraints is shown through a series of wind tunnel experiments. The result of the experiments confirms that the outcome of the fin optimization problem exhibits the best performance among the test cases, which validates the proposed methodology for designing the fins of the airship.