A novel trilithium compound, Li3[B(C6H4O2){O(CH2CH2O)3CH3}2][N(SO2CF3)2]2 (1‐2.0), with solid‐state ionic conductivity was synthesized. The crystal structure of 1‐2.0 consists of the one‐dimensional ionic conduction paths. The paths were afforded as a result of the self‐assembled stacking of the component molecules of 1‐2.0 with channel structures containing lithium ions. In this supramolecule, one lithium ion holds the component molecules in specific positions to construct a supramolecular structure with thermally stable ionic conduction paths and the others behave as carrier ions exhibiting selective lithium‐ion conductivity. Owing to the existence of both roles for the lithium ions, this electrolyte shows selective lithium‐ion conductivity.