Developing ionic materials with both high ionic conductivity and mechanical robustness remains challenging. Here, we present a polyampholyte elastomer based on ionic dimers (IDs) with strong imidazolium–sulfonate interactions. Polymerization of crosslinkable ID monomers yields a mechanically robust and ionically conductive ID elastomer (IDE). Incorporation of lithium salts increases the ionic conductivity to 0.82 mS cm⁻¹ with a high Li⁺ transference number of 0.79. The Li-containing IDE exhibits excellent mechanical properties, including a tensile strength of 27.4 MPa and a Young’s modulus of 211 MPa. A resistive iontronic sensor based on the IDE shows high sensitivity (gauge factor = 2.92) and stable operation over ~400 cycles. In addition, the IDE functions as a polymer electrolyte in a pouch-type full cell, delivering stable capacity at 1.0 C under ambient conditions.