  M101 is an ideal target in which to test predictions of massive star birth
and evolution. The large abundance gradient across M101 (a factor of 20)
suggests that many more WR stars must be found in the inner parts of this
galaxy than in the outer regions. Many HII regions and massive star-forming
complexes have been identified in M101; they should be rich in WR stars, and
surrounded by RSG stars. Finally, the Wolf-Rayet stars in M101 may be abundant
enough for one to explode as a Type Ib or Ic supernova and/or GRB within a
generation. The clear identification of the progenitor of a Type Ib or Ic
supernova as a WR star would be a major confirmation of current stellar
evolution theory.
  Motivated by these considerations, we have used the Hubble Space Telescope to
carry out a deep, HeII optical narrowband imaging survey of the massive star
populations in the ScI spiral galaxy M101. Combined with archival broadband
images, we were able to image almost the entire galaxy with the unprecedented
depth and resolution that only HST affords.
  We describe the extent of the survey and our images, as well as our data
reduction procedures. A detailed study of a field east of the center of M101,
containing the giant star-forming region NGC 5462, demonstrates how we find
candidates, their properties and spatial distribution, and how we rule out most
contaminants. The spatial distributions of the WR and RSG stars near a giant
star-forming complex are strikingly different. WR stars dominate the complex
core, while RSG dominate the complex halo. Future papers in this series will
describe and catalog more than a thousand WR and RSG candidates that are
detectable in our images, as well as spectra of many of those candidates.
