  Context. Wolf Rayet/black hole binaries are believed to exist as a later
evolutionary product of high-mass X-ray binaries. Hundreds of such binaries may
exist in galaxies, but only a few of them are close enough to be observed as
X-ray binaries. Only a couple of candidates have been reported so far. Aims.
Based on XMM-Newton observations, we report the positional coincidence of the
brightest X-ray source in NGC 300 (NGC 300 X-1) with a Wolf-Rayet candidate.
Temporal and spectral analysis of the X-ray source is performed. Methods. We
determine an accurate X-ray position of the object, and derive light curves,
spectra and flux in four XMM-Newton observations. Results. The positions of the
X-ray source and the helium star candidate coincide within 0.11"+-0.45". The
X-ray light curves show irregular variability. During one XMM-Newton
observation, the flux increased by about a factor of ten in 10 hours. The
spectrum can be modelled by a power-law with Gamma~2.45 with additional
relatively weak line emission, notably around 0.95 kev. The mean observed
(absorbed) luminosity in the 0.2-10 kev band is ~2x10^38 erg/s. Conclusions.
NGC 300 X-1 is a good candidate for a Wolf-Rayet/black-hole X-ray binary: its
position coincides with a Wolf-Rayet candidate and the unabsorbed X-ray
luminosity reached L(0.2-10 kev)~1x10^39 erg/s, suggesting the presence of a
black hole.
