Based on (1.0087 ± 0.0044) × 1010 J/ψ events collected with the BESIII detector at the BEPCII e+e− storage ring, we search for
$$ {K}_S^0 $$
invisible decays via the J/ψ →
$$ \phi {K}_S^0{K}_S^0 $$
process. No significant signal is observed, and the upper limit of the branching fraction of these invisible decays is set at 8.4 × 10−4 at the 90% confidence level. This is the first experimental search for
$$ {K}_S^0 $$
invisible decays.
