AbstractFlexible and bio‐integrated electronics have attracted great attention due to their enormous contributions to personalized medical devices. Power sources, serving as one of the most important components, have been suffering from many problems, including deficient biocompatibility, poor stretchability, and unstable electrical outputs under deformed conditions, which limits the practical applications in flexible and bio‐integrated electronics. Here, we reported a fully stretchable magnesium (Mg)–air battery based on dual‐ions‐conducting hydrogels (SDICH). The high‐performance battery enables long‐term operation with lighting 120 lighting emitting diodes (LEDs) for over 5 h. Benefiting from the advanced materials and mechanical designs, the battery exhibits stability electrical outputs under stretching, which allows to operate ordinarily under various mechanical deformations without performance decay. Furthermore, the great biocompatibility of the battery offers great opportunity for biomedical applications, which is demonstrated by a self‐adaption wound dressing system. The in vitro and in vivo results prove that the self‐adaption wound dressing can effectively prevent wound inflammation and promote wound healing. By exploiting thermal feedback mechanics, the system can adjust antibiotic release rate and dosage spontaneously according to the real‐time wound conditions. The proposed fully stretchable Mg–air battery and self‐adaption wound dressing display great potential in skin‐integrated electronics and personalized medicine.image