  We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey
(STAGES). STAGES is a multiwavelength project designed to probe physical
drivers of galaxy evolution across a wide range of environments and luminosity.
A complex multi-cluster system at z~0.165 has been the subject of an 80-orbit
F606W HST/ACS mosaic covering the full 0.5x0.5 (~5x5 Mpc^2) span of the
supercluster. Extensive multiwavelength observations with XMM-Newton, GALEX,
Spitzer, 2dF, GMRT, and the 17-band COMBO-17 photometric redshift survey
complement the HST imaging. Our survey goals include simultaneously linking
galaxy morphology with other observables such as age, star-formation rate,
nuclear activity, and stellar mass. In addition, with the multiwavelength
dataset and new high resolution mass maps from gravitational lensing, we are
able to disentangle the large-scale structure of the system. By examining all
aspects of environment we will be able to evaluate the relative importance of
the dark matter halos, the local galaxy density, and the hot X-ray gas in
driving galaxy transformation. This paper describes the HST imaging, data
reduction, and creation of a master catalogue. We perform Sersic fitting on the
HST images and conduct associated simulations to quantify completeness. In
addition, we present the COMBO-17 photometric redshift catalogue and estimates
of stellar masses and star-formation rates for this field. We define galaxy and
cluster sample selection criteria which will be the basis for forthcoming
science analyses, and present a compilation of notable objects in the field.
Finally, we describe the further multiwavelength observations and announce
public access to the data and catalogues.
