  We present the earliest ever ultraviolet spectrum of a gamma-ray burst (GRB)
as observed with the Swift-UVOT. The GRB 081203A spectrum was observed for 50
seconds with the UV grism starting 251 seconds after the Swift-BAT trigger when
the GRB was of u ~13.4 mag and still rising to its peak optical brightness. The
UV grism spectrum shows a damped Ly-alpha line, Ly-beta, and the Lyman
continuum break at a redshift z = 2.05 +/- 0.01. A model fit to the Lyman
absorption implies log N(HI) = 22.0 +/- 0.2 cm-2, which is typical for GRB host
galaxies with damped Ly-alpha absorbers. This observation of GRB 081203A
demonstrates that for GRBs brighter than v ~14 mag and with 0.5 < z < 3.5 the
UVOT will be able to provide redshifts, and probe for damped Ly-alpha absorbers
within 4-6 minutes from the time of the Swift-BAT trigger.
