  We report the discovery of a fifth image in the large separation lensed
quasar system SDSS J1004+4112. A faint point source located 0.2'' from the
center of the brightest galaxy in the lensing cluster is detected in images
taken with the Advanced Camera for Surveys (ACS) and the Near Infrared Camera
and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope. The flux
ratio between the point source and the brightest lensed component in the ACS
image is similar to that in the NICMOS image. The location and brightness of
the point source are consistent with lens model predictions for a lensed image.
We therefore conclude that the point source is likely to be a fifth image of
the source quasar. In addition, the NICMOS image reveals the lensed host galaxy
of the source quasar, which can strongly constrain the structure of the lensing
critical curves and thereby the mass distribution of the lensing cluster.
