In particle physics, the neutralino is a hypothetical particle and part of the doubling of the menagerie of particles predicted by supersymmetric theories.

Since the superpartners of the Z boson (zino), the photon (photino) and the neutral higgs (higgsino) have the same quantum numbers, they mix to form a particle called simply the neutralino. Virtually undetectable, it participates only in weak and gravitational interactions. Of the weakly-interacting massive particles (WIMPs) under consideration, the neutralino, as the lightest electrically neutral supersymmetric particle (at 30-5000 proton masses), is the leading candidate for cold dark matter.