IJPHM Special issue on Wind Turbine PHM is the first special issue that discusses the state-of-the-art in PHM of wind turbine systems. This Special Issue contains 14 excellent papers that highlight a wide range of current research and application topics related to wind turbine PHM. Fault diagnostics is an important aspect of wind turbine PHM. Eight papers included in this special issue deal with fault diagnostics of different parts of a wind turbine. Each of these papers presents different fault diagnostic techniques and sensing technologies.