  We discuss proton and neutron decays involving three leptons in the final
state. Some of these modes could constitute the dominant decay channel because
they conserve lepton-flavor symmetries that are broken in all usually
considered channels. This includes the particularly interesting and rarely
discussed $p\to e^+ e^+ \mu^-$ and $p\to \mu^+ \mu^+ e^-$ modes. As the
relevant effective operators arise at dimension 9 or 10, observation of a
three-lepton mode would probe energy scales of order 100 TeV. This allows to
connect proton decay to other probes such as rare meson decays or collider
physics. UV completions of this scenario involving leptoquarks unavoidably
violate lepton flavor universality and could provide an explanation to the
recent $b\to s\mu\mu$ anomalies observed in $B$ meson decays.
