  With the compelling evidence for massive neutrinos from recent
neutrino-oscillation experiments, one of the most fundamental tasks of particle
physics over the next years will be the determination of the absolute mass
scale of neutrinos. The absolute value of neutrino-masses will have crucial
implications for cosmology, astrophysics and particle physics. We present the
case for a next generation tritium beta decay experiment to perform a high
precision direct measurement of the absolute mass of the electron neutrino with
sub-eV sensitivity. We discuss the experimental requirements and technical
challenges of the proposed Karlsruhe Tritium Neutrino experiment (KATRIN) and
outline its physics potential.
