Elastomerically deformable fiber typed supercapacitors without performance loss are sought for such applications as power sources for micro-devices, wearable electronics, and implantable medical devices. Previously reported yarn and fiber supercapacitors are expensive to fabricate, difficult to upscale, or non-stretchable, which limits advanced use. Therefore, we developed elastomeric solid-state supercapacitors which are made by using giant inserted twist to coil a nylon sewing thread that is helically wrapped with a carbon nanotube sheet, and then electrochemically depositing pseudocapacitive MnO2 nanofibers. These solid-state supercapacitors can retain a specific capacitance when reversibly stretched by over 100% in the fiber direction, and largely retain capacitance while being dynamically stretched during charge and discharge process. The maximum linear and areal capacitances (based on active materials) and areal energy storage and power densities (based on overall supercapacitor dimensions) are high, despite of the engineered superelasticity of the fiber supercapacitor. Retention of supercapacitor performance during 50% strain, elastic deformation is demonstrated for supercapacitors incorporated into the wristband of a glove. Since we have deployed the utilized the twist-insertion-based coiling method to obtain highly elastomeric behaviors for other diverse high strength monofilament and multifilament polymer fibers (like polyethylene, Kevlar, silver-plated nylon 6, polyester, polypropylene, and polyvinylidene difluoride), the presently described supercapacitor fabrication method can be extended to supercapacitors that operate at high temperatures and use either hydrophilic or hydrophobic electrolytes.