<p>Hydrogels have garnered extensive interest owing to their exceptional flexibility, stimulus responsiveness, and outstanding biocompatibility. Nevertheless, the broad application of conventional hydrogels has been limited by the challenge of integrating robust mechanical strength, high ionic conductivity, and durability into a single material. In this work, a double-network hydrogel exhibiting high strength and high ionic conductivity and durability was developed by strategically modulating the assembly sequence of the two network layers and incorporating cellulose nanofibers (CNFs) and Fe³⁺ into the gel matrix. The resulting PVA/PAM/CNF/Fe³⁺ dual-network hydrogel leverages hydrogen bonding among polyvinyl alcohol (PVA), polyacrylamide (PAM), and CNF, in combination with coordination interactions with Fe³⁺, to form a cohesive network structure. This unique architecture endows the hydrogel with remarkable mechanical properties (fracture strength of 3.44 MPa), high stretchability (tensile strain of 587.8%), superior ionic conductivity (1.15 S/m), and high sensitivity (gauge factor of 9.40), along with excellent durability over 300 cycles. Furthermore, the hydrogel can be employed for real-time monitoring of human body movements, demonstrating its potential as a flexible wearable sensor. This study offers a novel strategy for designing high-strength, highly ionic double-network hydrogels and advances the development of flexible wearable electronic devices.</p>