The neutrinos emitted from supernovae contain information about the physics of stellar collapse and of the nature of the neutrinos themselves. Several large detectors exist that will be capable of observing some subset of those neutrinos. In addition, we have designed OMNIS, the Observatory for Multiflavour NeutrInos from Supernovae. OMNIS will detect the neutrinos from (a) neutral-current interactions from ν_e, ν_μ, , ν_τ and , and (b) charged-current interactions from high-momentum ν_e, with lead nuclei. It will utilize two types of detectors: (1) lead slabs alternating with vertical planes of neutron detectors, in which neutrons produced by neutrino–lead interactions will be detected, and (2) lead perchlorate, in which both the resulting neutrons and Cerenkov light will be detected. OMNIS will measure neutrino masses below 100 eV, provide new information on MSW or vacuum oscillations from ν_μ/ν_τ to ν_e, especially to Θ₁₃, and possibly diagnose the process of collapse to a black hole. It will observe the late-time evolution of the neutrino distributions, and possibly see predicted late-time effects, e.g. a phase transition from neutron-star matter to kaon-condensed matter or quark matter. OMNIS is also sensitive to some modes of nucleon decay that should make it possible to improve significantly on present limits for those modes. Of crucial importance to OMNIS is an experiment, using neutrinos from a stopped pion beam, to determine the flavour and energy-dependent response of lead to neutrinos. This will provide important input into cross section calculations for which few data currently exist. We plan to perform this experiment using one of the lead perchlorate detector modules from OMNIS.