  We report the first observation of double radiative capture on pionic
hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC
spectrometer, and detected $\gamma$--ray coincidences following $\pi^-$ stops
in liquid hydrogen. We found the branching ratio for double radiative capture
to be $(3.05 \pm 0.27(stat.) \pm 0.31(syst.)) \times 10^{-5}$. The measured
branching ratio and angle-energy distributions support the theoretical
prediction of a dominant contribution from the $\pi \pi \to \gamma \gamma$
annihilation mechanism.
