Single-ion polymer electrolytes are expected to play an important role in the development of next-generation lithium metal batteries. In this paper, the synthesis and characterization of single-ion conducting polyurethanes (SIPUs) based on PEG and a specifically designed ionic liquid monomer (bis-MPTFSI) is presented. Exploiting the flexible chemistry of polyurethanes, it was possible to tailor the composition and chemical structure of SIPE, obtaining both segmented and crosslinked lithium ion-conductive (σ = 10⁻⁸−10⁻⁴ S cm⁻¹) and free-standing films with the lithium transference number close to unity. Finally, the performances of gel polymer electrolytes based on SIPUs for lithium metal batteries operating at room temperature were investigated (80 cycles at C/10 with nearly 100% efficiency). To the best of our knowledge, these SIPUs represent one of the first examples of polyurethane-based poly(ionic liquid)s for application in the field of battery science.