Searches for invisible new particles at Belle II

Belle~II has unique sensitivity for a broad class of models postulating the existence of dark matter particles with masses in the MeV–GeV range. We present recent world-leading results from Belle~II searches for several non-SM particles. These include production of $Z^{\mathrm{\prime }}$ bosons, axion-like particles, and dark scalars in association with two muons in $e^{+}{e}^{-}$ collisions; long-lived (pseudo)scalars produced in decays of $\mathit{\text{B}}$-mesons; and invisible particles produced in decays of $\tau$ leptons.