AbstractBromide‐ion batteries can provide higher energy densities compared to conventional lithium‐ion batteries, but the high water solubility of bromide salts may require all‐solid‐state cells. Fortunately, the low Young's modulus of bromide salts is an advantage in terms of fabricating high‐performance all‐solid‐state cells. The present study provides the first‐ever demonstration of an all‐solid‐state bromide‐ion battery. In this work, a novel, single‐phase, K‐doped PbBr2 electrolyte was prepared by mechanical milling, and highly dense pellets were readily obtained from this material by uniaxial cold pressing, because of its low modulus. An initial discharge capacity equal to 87 % of the theoretical capacity was exhibited by an experimental battery when using a BiBr3 positive electrode. This concept of a bromide shuttle battery is expected to promote the research of next‐generation batteries incorporating new active materials and based on conversion‐type reactions.