Аннотация:A search for K0S(L)→μ+μ−μ+μ− decays is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb−1. No evidence for signal is found. The 90\% confidence level upper limits are the first set for both decays and are B(K0S→μ+μ−μ+μ−)<5.1×10−12 and B(K0L→μ+μ−μ+μ−)<2.3×10−9.