High-performance stretchable energy storage devices are urgently needed due to the rapid development of portable, wearable, and stretchable electronics. However, most of the stretchable single-cell energy storage devices suffer from a relatively low operating voltage and thus a low energy density. Here, we report an all-solid-state asymmetric stretchable supercapacitor (ASS) with high energy density using the wrinkled manganese dioxide (MnO₂)/carbon nanotube (CNT) hybrid film as a positive electrode and the wrinkled iron oxide (Fe₂O₃)/CNT composite film as a negative electrode in a neutral Na₂SO₄–poly(vinyl alcohol) (Na₂SO₄/PVA) gel electrolyte. Due to the high specific capacitance and excellent rate performance of MnO₂/CNTs and Fe₂O₃/CNTs, as well as the synergistic effects of the two electrodes with an optimized potential window, the asymmetric stretchable cell exhibits superior electrochemical and mechanical performances. An optimized ASS can be reversibly cycled in the voltage window between 0 and 2 V, and shows a supreme energy density of 45.8 W h kg⁻¹ (corresponding power density of 0.41 kW kg⁻¹). Additionally, the ASS also exhibits exceptional cycling stability and durability, with 98.9% specific capacitance retained even after 10 000 electrochemical cycles at multiple strains. These encouraging results show its great potential in developing stretchable energy storage devices with high energy and power densities for wearable and implantable electronic applications.