Searches for Lepton Flavour Violation at ATLAS and CMS

Lepton flavour violation (LFV), and lepton flavour university violation (LFUV), are striking signatures of beyond the Standard Model (BSM) physics. Recent searches for these at the ATLAS and CMS experiments are presented, using proton-proton collisions with a centre of mass energy of 13 TeV. A range of models and signatures are considered, including leptoquarks, heavy neutral leptons, LFV in $\tau$ lepton decays, and new measurements of $R(K)$ and $R(J\mathrm{/}\mathrm{\Psi })$.