  We report the identification of a cluster of galaxies around the
high-redshift radio galaxy 3CR184 at z = 0.996. The identification is supported
by an excess of galaxies observed in projection in I band images (both in
ground-based and HST data), a peak in the redshift distribution comprising 11
galaxies (out of 56 with measured redshifts) in a ~2000 km/s velocity interval,
and the observation on HST WFPC2 frames of a gravitational arc seen projected
at 42kpc away from the central radio galaxy. We thus have strong evidence for
the presence of a massive cluster at z~1.
