  We report on the highest energy photons from the Crab Nebula observed by the
Tibet air shower array with the underground water-Cherenkov-type muon detector
array. Based on the criterion of muon number measured in an air shower, we
successfully suppress 99.92% of the cosmic-ray background events with energies
$E>100$ TeV. As a result, we observed 24 photon-like events with $E>100$ TeV
against 5.5 background events, which corresponds to 5.6$\sigma$ statistical
significance. This is the first detection of photons with $E>100$ TeV from an
astrophysical source.
