  We report the discovery of an almost complete Einstein ring of diameter 10"
in Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Spectroscopic data
from the 6m telescope of the Special Astrophysical Observatory reveals that the
deflecting galaxy has a line-of-sight velocity dispersion in excess of 400 km/s
and a redshift of 0.444, whilst the source is a star-forming galaxy with a
redshift of 2.379. From its color and luminosity, we conclude that the lens is
an exceptionally massive Luminous Red Galaxy (LRG) with a mass within the
Einstein radius of 5 x 10^12 solar masses. This remarkable system provides a
laboratory for probing the dark matter distribution in LRGs at distances out to
3 effective radii, and studying the properties of high redshift star-forming
galaxies.
