  The intense, bursting X-ray source in the globular cluster NGC 1851 was one
of the first cluster sources discovered, but has remained optically
unidentified for 25 years. We report here on results from Hubble Space
Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution
images resolve ~200 objects in the 3'' radius Einstein X-ray error circle, 40
times as many as in previous ground-based work. A color-magnitude diagram of
the cluster clearly reveals a markedly UV-excess object with B~21, (U-B) ~ -0.9
only 2'' from the X-ray position. The UV-excess candidate is 0.12'' distant
from a second, unremarkable star that is 0.5 mag brighter in B; thus
ground-based studies of this field are probably impractical. Three other
UV-excess objects are also present among the ~16,000 objects in the surveyed
region of the cluster, leaving a ~5% probability that a UV-excess object has
fallen in the X-ray error circle by chance. No variability of the candidate is
seen in these data, although a more complete study is required. If this object
is in fact the counterpart of the X-ray source, previous inferences that some
globular cluster X-ray sources are optically subluminous with respect to
low-mass X-ray binaries in the field are now strengthened.
