Rare kaon decays are mediated through flavour changing neutral currents
arising through W-W and Z/gamma exchange diagrams. In the Standard Model these
decays are hugely suppressed 2nd order electroweak processes and therefore ideal probes for new physics. Some decay channels receive contributions from hadronic long-distance effects which we aim to predict using lattice QCD. This talk reviews recent progress and highlights the major challenges that need to be overcome.