  We present the first lattice-QCD calculation of the kaon valence-quark
distribution functions using the large-momentum effective theory (LaMET)
approach. The calculation is performed with multiple pion masses with the
lightest one around 220 MeV, 2 lattice spacings $a=0.06$ and 0.12 fm,
$(M_\pi)_\text{min} L \approx 5.5$, and high statistics ranging from 11,600 to
61,312 measurements. We also calculate the valence-quark distribution of pion
and find it to be consistent with the FNAL E615 experimental results, and our
ratio of the $u$ quark PDF in the kaon to that in the pion agrees with the CERN
NA3 experiment. We also make predictions of the strange-quark distribution of
the kaon.
