  We report the discovery of only the fourth massive WO star to be found in the
Milky Way, and only the seventh identified within the Local Group. This has
resulted from the first observations made in a programme of follow-up
spectroscopy of candidate emission line stars from the AAO/UK Schmidt Southern
Galactic Plane H-alpha Survey. The optical spectrum of this star, to become WR
93b in the Catalogue of Galactic Wolf-Rayet stars, is presented and described.
WR 93b is classified as WO3 and is shown to be highly reddened (E(B-V) = 2.1 pm
0.1). A recombination line analysis of the emission lines yields the abundance
ratios C/He = 0.95 and O/He = 0.13 (by number). Comparisons at near infrared
wavelengths of reddening corrected photometry between WR 93b and both of Sand 2
(WO3, D = 49 kpc) and Sand 5 (WO2, D = 1.75 kpc) yields a consistent distance
to WR 93b of 3.4 kpc. Positioned at Galactic co-ordinates l = 353.27, b =
-0.85, the star is most likely located in the Scutum-Crux Arm of the inner
Milky Way. We note that none of the four Galactic WO stars lies significantly
beyond the Solar Circle (with two well inside). Estimation of the wind terminal
velocity in WR 93b at 5750 km/s makes this star the current wind speed record
holder among all non-degenerate stars.
