  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
$R(J/\Psi)$.
