Abstract Regarding the complex properties of various cations, the design of aqueous batteries that can simultaneously store multi‐ions with high capacity and satisfactory rate performance is a great challenge. Here an amorphization strategy to boost cation‐ion storage capacities of anode materials is reported. In monovalent (H + , Li + , K + ), divalent (Mg 2+ , Ca 2+ , Zn 2+ ) and even trivalent (Al 3+ ) aqueous electrolytes, the capacity of the resulting amorphous MoO x is more than quadruple than that of crystalline MoO x and exceeds those of other reported multiple‐ion storage materials. Both experimental and theoretical calculations reveal the generation of ample active sites and isotropic ions in the amorphous phase, which accelerates cation migration within the electrode bulk. Amorphous MoO x can be coupled with multi‐ion storage cathodes to realize electrochemical energy storage devices with different carriers, promising high energy and power densities. The power density exceeded 15000 W kg −1 , demonstrating the great potential of amorphous MoO x in advanced aqueous batteries.