  We present Keck/NIRSPEC near-IR images and Magellan/IMACS optical
spectroscopy of the host galaxy of GRB 031203. The host is an actively
star-forming galaxy at z=0.1055 +/- 0.0001. This is the lowest redshift GRB
to-date, aside from GRB 980425. From the hydrogen Balmer lines, we infer an
extinction of A_V = 3.62 +/- 0.25 or a total reddening E_T(B-V) = 1.17 +/- 0.1
toward the sightline to the nebular regions. After correcting for reddening, we
perform an emission-line analysis and derive an ISM temperature of
T=13400+/-2000K and electron density of n_e = 300 cm^(-3). These imply a
metallicity [O/H]=-0.72+/-0.15 dex and a roughly solar abundance pattern for N,
Ne, S, and Ar. Integrating Ha, we infer a dust-corrected star formation rate
(SFR) of > 11 Msol/yr. These observations have the following implications: (1)
the galaxy has a low K'-band luminosity L ~ L^*/5, typical of GRB host
galaxies; (2) the low redshift indicates GRB 031203 had an isotropic-equivalent
gamma-ray energy release smaller than all previous confirmed GRB events. The
burst discovery raises the likelihood of identifying many additional low z, low
flux events with Swift; (3) the large SFR, low metallicity, and the inferred
hard radiation field is suggestive of massive star formation, supporting the
collapsar model; (4) several lines of evidence argue against the identification
of GRB 031203 as an X-ray flash event.
