  The Fermi Gamma-ray Space Telescope has revolutionized our knowledge of the
gamma-ray pulsar population, leading to the discovery of almost 100 gamma-ray
pulsars and dozens of gamma-ray millisecond pulsars (MSPs). Although the
outer-gap model predicts different sites of emission for the radio and
gamma-ray pulsars, until now all of the known gamma-ray MSPs have been visible
in the radio. Here we report the discovery of a "radio-quiet" gamma-ray
emitting MSP candidate by using Fermi, Chandra, Swift, and optical
observations. The X-ray and gamma-ray properties of the source are consistent
with known gamma-ray pulsars. We also found a 4.63-hr orbital period in optical
and X-ray data. We suggest that the source is a black widow-like MSP with a
~0.1 solar-mass late-type companion star. Based on the profile of the optical
and X-ray light-curves, the companion star is believed to be heated by the
pulsar while the X-ray emissions originate from pulsar magnetosphere and/or
from intra-binary shock. No radio detection of the source has been reported yet
and although no gamma-ray/radio pulsation has been found, we estimated that the
spin period of the MSP is ~3-5 ms based on the inferred gamma-ray luminosity.
