In a world with fast growing popularity of renewable energy, wind turbines hold a significant place. The constant quest for efficiency requires careful and clever thinking in the wind turbine design. The wind turbine blade, being at the first stage of energy conversion, plays a major role in the overall efficiency of the system. This book explains the various aerodynamic principles and structural considerations behind the blade design. With a case study of 1.2MW Horizontal Axis Wind Turbine blade, this work looks at how the theory is put into practice. The use of composite material in the blade construction is also addressed in the case study. It should be good knowledge for anyone who is interested in or concerned with the mechanical design of wind turbines with a basic knowledge of fluid dynamics and structural mechanics.