With the rapidly approaching implementation of wearable electronic devices such as implantable devices, stretchable sensors, and healthcare devices, stretchable power sources have aroused worldwide attention as a key component in this emerging field. Among stretchable power sources, batteries, which store electrical energy through redox reactions during charge/discharge processes, are an attractive candidate because of their high energy density, high output voltage, and long-term stability. In recent years, extensive efforts have been devoted to developing new materials and innovative structural designs for stretchable batteries. This review covers the latest advances in stretchable batteries, focusing on advanced stretchable materials and their design strategies. First, we provide a detailed overview of the materials aspects of components in a stretchable battery, including electrode materials, solid-state electrolytes, and stretchable separator membranes. Second, we provide an overview on various structural engineering strategies to impart stretchability to batteries (i. e., wavy/buckling structures, island-bridge structures, and origami/kirigami structures). Third, we summarize recently reported developments in stretchable batteries based on various chemistries, including Li-based batteries, multivalent-based batteries, and metal-air batteries. Finally, we discuss the future perspectives and remaining challenges toward the practical application of stretchable batteries with reliable mechanical robustness and stable electrochemical performance under a physical strain.