Ever‐increasing energy demands call for alternative energy storage technologies with balanced performance and cost characteristics to meet current and emerging applications. Dual‐ion batteries (DIBs) are considered particularly attractive owing to the potentially high specific energy, a rich variety of charge carrier combinations, and the applicability of metal‐free cathode and earth‐abundant anode materials. However, their performance falls far below expectations because of a large excess of solvent needed to dissolve electroactive species that induces side reactions and contributes parasitic weight, which penalizes the reversible capacity and cell‐level energy density. Herein, a solvent‐free DIB utilizing a binary alkali metal molten salt based on bis(fluorosulfonyl)amide as the electrolyte to solve these issues is demonstrated. The cell (NaK‐DIB) operates in a temperature range of 90–120 °C and exhibits high theoretical energy densities of 246 Wh kg−1 and 533 Wh L−1 based on active materials and capacity‐matched electrolyte, far surpassing those of reported DIBs. Further improvements could realize affordable grid‐scale energy storage. Solvent‐free dual‐ion batteries of both high energy density and high safety are demonstrated with the utilization of an inorganic molten salt as the electrolyte. The new cell chemistry inherits the dendrite‐free characteristic of liquid metal anodes and the favored electrode kinetics and thermal robustness of molten‐salt batteries, paving the way for affordable large‐scale energy storage.