  In this paper we present a spectral atlas covering the wavelength interval
930--1188A for O2--O9.5 stars using Far Ultraviolet Spectroscopic Explorer
archival data. The stars selected for the atlas were drawn from three
populations: Galactic main sequence (class III-V) stars, supergiants, and main
sequence stars in the Magellanic Clouds, which have low metallicities. For each
of these stars we have prepared FITS files comprised of paris of merged spectra
for user access via the Multi-Mission Archives at Space Telescope. We chose
spectra from the first population with spectral types O4, O5, O6, O7, O8, and
O9.5 and used them to compile tables and figures with identifications of all
possible atmospheric and ISM lines in the region 949-1188A. Our identified line
totals for these six representative spectra are 821 (500), 992 (663), 1077
(749), 1178 (847), 1359 (1001), and 1798 (1392) lines, respectively, where the
numbers in parentheses are the totals of lines formed in the atmospheres,
according to spectral synthesis models. The total number of unique atmospheric
identifications for the six main sequence O star template spectra is 1792,
whereas the number of atmospheric lines in common to these spectra is 300. The
number of identified lines decreases toward earlier types (increasing effective
temperature), the whlle percentages of "missed" features (lines not predicted
from our spectral syntheses) drops from a high of 8% at type B0.2, from our
recently published B star far-UV atlas, to 1--3% for type O spectra. The
percentages of overpredicted lines are similar, despite their being much higher
for B star spectra. We also discuss the statistics of line populations among
the various elemental ionization states. Finally, as an aid to users we list
those isolated lines that can be used to determine stellar temperatures and the
presence of possible chemical anomalies.
