  We consider the decay of positronium to a neutrino-antineutrino accompanied
by a single photon. Since the neutrino pair go undetected, this appears as a
single photon decay of positronium. These decay channel are mediated through
the exchange of the massive $W$ and $Z$ vector bosons of the electroweak
interaction. After summing over the various neutrino channels, the standard
model calculation yields the rate for such a single photon decay process of
$\Gamma_{Ps \rightarrow \gamma}$ = 1.72 $\times 10^{-19}$ s$^{-1}$.
