  We propose the Hyper-Kamiokande (Hyper-K) detector as a next generation un-
derground water Cherenkov detector. It will serve as a far detector of a long
base- line neutrino oscillation experiment envisioned for the upgraded J-PARC
beam, and as a detector capable of observing, far beyond the sensitivity of the
Super-Kamiokande (Super-K) detector, proton decays, atmospheric neutrinos, and
neutrinos from astro- physical origins. The current baseline design of Hyper-K
is based on the highly suc- cessful Super-K detector, taking full advantage of
a well-proven technology. Hyper-K consists of two cylindrical tanks lying
side-by-side, the outer dimensions of each tank being 48(W) x54(H) x 250(L) m3.
The total (fiducial) mass of the detector is 0.99 (0.56) million metric tons,
which is about 20 (25) times larger than that of Super-K.
  This set of three one- page whitepapers prepared for the US Snowmass process
describes the opportunities for future physics discoveries at the Hyper-K
facility with beam, atmospheric and astrophysical neutrinos.
