Some highlights of the first four years of the Fermi Gamma-ray Space Telescope

The Fermi Gamma-ray Space Telescope, formerly called GLAST, measures the cosmic gamma-ray flux in the energy range 8 keV to > 300 GeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20% of the sky at any instant, and the entire sky on a timescale of a few hours. With its launch in 2008, Fermi opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and the origins of cosmic rays, and searches for hypothetical new phenomena such as particle dark matter annihilations. A brief overview and selected science highlights from the first four years are provided.