  We present revised infrared (2.2 micron) astrometry of the field containing
the Galactic microquasar GRS 1758-258, using observations at the Keck I 10-m
telescope. We find three candidates for the microquasar within a 3 sigma error
circle, but none within 2 sigma. We show that if the 18.4 day X-ray period of
GRS 1758-258 is due to a binary orbit, then only one of the three candidates,
an early K-type giant, is large enough to power the microquasar via Roche lobe
overflow. We therefore identify this star as the infrared counterpart of GRS
1758-258, which we classify as a low mass X-ray binary. Long term infrared
monitoring of this source should provide further information about the
microquasar system, including a confirmation of the X-ray period and an
estimate of the compact object's mass.
