  We report on a bright flare in the Crab Nebula detected by the Large Area
Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The period of
significantly increased luminosity occurred in 2013 March and lasted for
approximately 2 weeks. During this period, we observed flux variability on
timescales of approximately 5\,hours. The combined photon flux above 100 MeV
from the pulsar and its nebula reached a peak value of $(12.5\pm 0.8)\cdot
10^{-6}$\,cm$^{-2}$\,s$^{-1}$ on 2013 March 6. This value exceeds the average
flux by almost a factor of 6 and implies a $\sim20$ times higher flux for the
synchrotron component of the nebula alone. This is the second brightest flare
observed from this source. Spectral and temporal analysis of the LAT data
collected during the outburst reveal a rapidly varying synchrotron component of
the Crab Nebula while the pulsar emission remains constant in time.
