Batteries assembled with lithium metal anodes and high-capacity cathodes-including air, sulfur, and lithium-rich transition metal oxides-have higher energy density than conventional Li-ion counterparts. Unfortunately, the lifetime of lithium-metal cells is typically short, owing to the formation of dendrites on charging, which eventually shorts the cells. Short cycle life is also observed when lithium deposits with a "mossy" morphology; the high surface area of mossy deposits increases the rate of electrolyte degradation, eventually drying out the cells. Here we show that a lithium-ion-conducting, architected macroporous polyelectrolyte (AMP-1) serves as a long-lasting host for uniform and dense lithium-metal electrodeposits. High Coulombic efficiencies indicate the low occurrence of parasitic reactions with the electrolyte. Galvanostatic discharge experiments indicate that AMP-1 suppresses dendrite formation, extending over 2-fold the short-circuit time at high current density. Our success opens new directions for lithium anode development for commercial cells.