  Using Hubble Space Telescope observations with STIS, we study the main
exciting stars of N81, a high excitation compact Hii region in the Small
Magellanic Cloud (SMC). These far UV observations are the first spectroscopic
measurements of stars in such a region and reveal features characteristic of an
O6-O8 stellar type. The astonishing weakness of their wind profiles and their
sub-luminosity (up to ~ 2 mag fainter in Mv than the corresponding dwarfs) make
these stars a unique stellar population in the Magellanic Clouds. Our analysis
suggests that they are probably in the Hertzsprung-Russell diagram locus of a
particularly young class of massive stars, the so-called Vz luminosity class,
as they are arriving on the zero age main sequence.
