  We present the first grating-resolution X-ray spectra of the Seyfert 1 galaxy
NGC 3783, obtained with the High Energy Transmission Grating Spectrometer on
the Chandra X-ray Observatory. These spectra reveal many narrow absorption
lines from the H-like and He-like ions of O, Ne, Mg, Si, S and Ar, as well as
FeXVII-FeXXI L-shell lines. We have also identified several weak emission
lines, mainly from O and Ne. The absorption lines are blueshifted by a mean
velocity of approximately 440\pm200 km/s and are not resolved, indicating a
velocity dispersion within the absorbing gas of a few hundred km/s or less. We
measure the lines' equivalent widths and compare them with the predictions of
photoionization models. The best-fitting model has a microturbulence velocity
of 150 km/s and a hydrogen column density of 1.3\times10^22 cm^-2. The measured
blueshifts and inferred velocity dispersions of the X-ray absorption lines are
consistent with those of the strongest UV absorption lines observed in this
object. However, simple models that propose to strictly unify the X-ray and UV
absorbers have difficulty explaining simultaneously the X-ray and UV absorption
line strengths.
