<p>Converting body heat into electricity presents an appealing route for sustainably powering wearable electronics; however, conventional thermoelectric materials face significant drawbacks, including high ionic concentrations, toxicity, and limited thermoelectric efficiency. Here, we report an ionic thermoelectric hydrogel designed through precise supramolecular chemistry, utilizing dual molecular interactions, host-guest complexation of α-cyclodextrin (α-CD) with I₃⁻ ions and hydrogen bonding between polyvinyl alcohol (PVA) polymer chains and I₃⁻. This molecularly tailored approach markedly amplifies thermoelectric performance, achieving a high thermopower of 2.21 mV/K and a tenfold enhancement in peak power output at an exceptionally low iodine concentration (10 mmol/L I⁻ + 2.5 mmol/L I₃⁻). The hydrogel maintains excellent biocompatibility and mechanical robustness, suitable for direct skin contact. Demonstrated applications include flexible thermoelectric devices generating nearly 100 mV from body heat and sensor arrays capable of motion and spatial temperature sensing. These results underscore the substantial potential of supramolecularly designed ionic thermoelectric hydrogels for wearable energy harvesting, personalized healthcare monitoring, and advanced human-computer interfaces.</p>