We use the WISE-2MASS infrared galaxy catalog matched with Pan-STARRS1 (PS1) galaxies to search for a supervoid in the direction of the Cosmic Microwave Background Cold Spot. Our imaging catalog has median redshift $z≃ 0.14$, and we obtain photometric redshifts from PS1 optical colours to create a tomographic map of the galaxy distribution. The radial profile centred on the Cold Spot shows a large low density region, extending over 10's of degrees. Motivated by previous Cosmic Microwave Background results, we test for underdensities within two angular radii, $5^∘$, and $15^∘$. The counts in photometric redshift bins show significantly low densities at high detection significance, $\gtrsim 5 σ$ and $\gtrsim 6 σ$, respectively, for the two fiducial radii. The line-of-sight position of the deepest region of the void is $z≃ 0.15-0.25$. Our data, combined with an earlier measurement by Granett et al. 2010, are consistent with a large $R_{\rm void}=(220 ± 50) h^{-1}Mpc $ supervoid with $δ_{m} ≃ -0.14 ± 0.04$ centered at $z=0.22±0.03$. Such a supervoid, constituting at least a $≃ 3.3σ$ fluctuation in a Gaussian distribution of the $Λ CDM$ model, is a plausible cause for the Cold Spot. ; Comment: 8 pages, 6 figures, accepted for publication by MNRAS