Abstract Solid polymer electrolytes (SPEs) offer an appealing alternative to volatile and flammable organic liquid electrolytes for high‐energy lithium metal batteries (LMBs). Despite their potential, two key challenges, insufficient ionic conductivity and inadequate interfacial performance, continue to hinder practical development. Here, the promising potential of a single‐ion conducting gel polymer electrolyte (SIGPE) derived from a polymerizable deep eutectic monomer (PDEM) is demonstrated. This structure forms dynamic nanophases with a high‐dielectric‐constant dielectricizer through Li + ‐bridged molecular self‐association within a flexible polymer matrix. This design regulates ion pathways to enable rapid Li + conduction, effectively preventing interfacial polarization and promoting ion dissociation, while also exhibiting viscoelastic properties that strengthen interface stability. The resultant SIGPE exhibits a high oxidation voltage of 5.0 V and a near‐unity transference number of 0.86. In the LFP|SIGPE|Li full cell, the formation of an inorganic‐rich SEI layer, driven by hetero species (Li 2 O/LiF), enables a high discharge capacity of 131.9 mAh g −1 at 1 C and stable cycling performance, with 71.9% capacity retention and 99.5% coulombic efficiency after 400 cycles at 1 C and 30 °C. These findings underscore the potential of PDEM‐based SIGPE to enhance performance, safety, and sustainability in LMBs, paving the way for practical use in high‐energy storage systems.