  The Herschel ATLAS is the largest open-time key project that will be carried
out on the Herschel Space Observatory. It will survey 510 square degrees of the
extragalactic sky, four times larger than all the other Herschel surveys
combined, in five far-infrared and submillimetre bands. We describe the survey,
the complementary multi-wavelength datasets that will be combined with the
Herschel data, and the six major science programmes we are undertaking. Using
new models based on a previous submillimetre survey of galaxies, we present
predictions of the properties of the ATLAS sources in other wavebands.
