  Observations of the long-duration Gamma-Ray Burst GRB 080916C by the Fermi
Gamma-ray Burst Monitor and Large Area Telescope show that it has a single
spectral form from 8 keV to 13.2 GeV. The E>100 MeV emission was ~5 s later
than the E<1 MeV emission and lasted much longer even after photons with E<100
MeV became undetectable. The redshift from GROND of z~4.35 means that this GRB
has the largest reported apparent isotropic gamma-ray energy release, E_{iso} ~
8.8 x10^{54} ergs. It also sets a stringent lower limit on the GRB outflow
Lorentz factor, Gamma_{min}~890, and limits the quantum gravity mass scale,
M_{QG} > 1.3 x 10^{18} GeV/c^2.
