  We propose that neutrino-proton elastic scattering, $\nu + p \to \nu + p$,
can be used for the detection of supernova neutrinos in scintillator detectors.
Though the proton recoil kinetic energy spectrum is soft, with $T_p \simeq 2
E_\nu^2/M_p$, and the scintillation light output from slow, heavily ionizing
protons is quenched, the yield above a realistic threshold is nearly as large
as that from $\bar{\nu}_e + p \to e^+ + n$. In addition, the measured proton
spectrum is related to the incident neutrino spectrum, which solves a
long-standing problem of how to separately measure the total energy and
temperature of $\nu_\mu$, $\nu_\tau$, $\bar{\nu}_\mu$, and $\bar{\nu}_\tau$.
The ability to detect this signal would give detectors like KamLAND and
Borexino a crucial and unique role in the quest to detect supernova neutrinos.
