  Hubble Space Telescope observations of the site of the supernova (SN) 2008ax
obtained in 2011 and 2013 reveal that the possible progenitor object detected
in pre-explosion images was in fact multiple. Four point sources are resolved
in the new, higher-resolution images. We identify one of the sources with the
fading SN. The other three objects are consistent with single supergiant stars.
We conclude that their light contaminated the previously identified progenitor
candidate. After subtraction of these stars, the progenitor appears to be
significantly fainter and bluer than previously measured. Post-explosion
photometry at the SN location indicates that the progenitor object has
disappeared. If single, the progenitor is compatible with a supergiant star of
B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in
the ultraviolet to account for the observations. Moreover, our hydrodynamical
modelling shows the pre-explosion mass was $4-5$ $M_\odot$ and the radius was
$30-50$ $R_\odot$, which is incompatible with a WR progenitor. We present a
possible interacting binary progenitor computed with our evolutionary models
that reproduces all the observational evidence. A companion star as luminous as
an O9-B0 main-sequence star may have remained after the explosion.
