  The nearby galaxy M33 hosts the most luminous steady X-ray source in the
Local Group. The high spatial resolution of Chandra allows us to confirm that
this ultra-luminous X-ray source is within the nucleus and rule out at the 4.6
sigma level a previously proposed possible counterpart located 1" away. The
X-ray spectrum is well fitted by a disc blackbody with kT=1.18+-0.02 keV and R
cos(theta)^(0.5}=57+-3 km, consistent with earlier results from ASCA and
BeppoSAX. The source flux is steady between 1 and 1e4 s (<3% rms variability,
0.5-10 keV) with a 0.5-10 keV luminosity of 1.5e39 erg/s. The X-ray properties
and an association with a radio source are reminiscent of the galactic
microquasar GRS 1915+105.
