Rare decays at LHCb

Flavour-changing neutral-current processes, such as $b\to s{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$, are forbidden at tree level in the Standard Model and hence might receive comparatively large corrections from new particles. This document highlights recent measurements from LHCb on $b\to s{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ and purely-leptonic decays, including tests of lepton flavour universality and searches for lepton flavour violation.