  We present a multi-wavelength study of the unassociated Fermi-LAT source,
3FGL J0954.8-3948, which is likely the gamma-ray counterpart of a 9.3-hour
binary in the field. With more than 9 years of Pass 8 LAT data, we updated the
gamma-ray spectral properties and the LAT localization of the gamma-ray source.
While the binary lies outside the cataloged 95% error ellipse, the optimized
LAT ellipse is 0.1 degrees closer and encloses the binary. The system is likely
spectrally hard in X-rays (photon index ~ 1.4) with orbital modulations
detected in optical, UV, and possibly X-rays. A steep spectrum radio
counterpart (spectral index ~ -1.6) is also found in the TIFR GMRT Sky Survey
(TGSS), implying that it is a pulsar system. We obtained a series of SOAR and
Gemini spectroscopic observations in 2017/2018, which show a low-mass secondary
orbiting in a close circular orbit with K2 = 272 km/s under strong irradiation
by the primary compact object. All the observations as well as the modelling of
the X/gamma-ray high-energy emission suggest that 3FGL J0954.8-3948 is a
redback millisecond pulsar in a rotation-powered state.
