In the hierarchical paradigm of structure formation, galaxy clusters are the largest objects ever to virialize. They are believed to grow by accreting mass through large scale, strong yet elusive, virial shocks. Such a collisionless shock is thought to accelerate relativistic electrons, thus generating a spectrally-flat leptonic virial ring. We detect a gamma-ray signal by stacking Fermi-LAT data for 112 clusters, enhancing the ring sensitivity by rescaling clusters to their virial radii and utilizing the anticipated spectrum. We also present evidence for gamma-ray and X-ray virial signatures in the nearby Coma cluster. These signals correspond to a fraction of about 0.005 (uncertain to within a factor of ~2) of the shocked energy deposited in relativistic electrons with a flat spectrum over a Hubble time. The results validate the shock paradigm, calibrate its parameters, gauge the evolution of cosmic-rays, and indicate that the cumulative emission from such shocks significantly contributes to the diffuse extragalactic gamma-ray and radio backgrounds.