  The Xi^0 muon semi-leptonic decay has been observed for the first time with
nine identified events using the KTeV beam line and detector at Fermilab. The
decay is normalized to the Xi^0 beta decay mode and yields a value for the
ratio of decay rates of $(1.8^{+0.7}_{-0.5}(stat.)\pm0.2(syst.))\times
10^{-2}$. This is in agreement with the SU(3) flavor symmetric quark model.
