AbstractDuring the past two decades, the vigorous development of flexible organic semiconductor devices has heralded a new era of human society due to their promising applications in portable, wearable, implantable, and biological electronics. In recent years, exciting progress has been made on various flexible electronic devices, including organic light‐emitting diodes, organic photovoltaics, organic thin‐film transistors, organic flexible integrated circuits, sensors, and memories. Here, to provide a comprehensive and up‐to‐date review on this emerging field, the focus is on the critical issues of organic devices, including material choice, device design, mechanical flexibility, strain effects, and processing techniques, as well as some specific applications that have been successfully developed. Finally, a conclusion and an outlook for the future development of this field are given.