  Fast Radio Bursts are millisecond bursts of radio radiation at frequencies of
about 1 GHz, recently discovered in pulsar surveys. They have not yet been
definitively identified with any other astronomical object or phenomenon. The
bursts are strongly dispersed, indicating passage through a high column density
of low density plasma. The most economical interpretation is that this is the
interglactic medium, indicating that FRB are at "cosmological" distances with
redshifts in the range 0.3--1.3. Their inferred brightness temperatures are as
high as $10^{37\,\circ}$K, implying coherent emission by "bunched" charges, as
in radio pulsars. I review the astronomical sites, objects and emission
processes that have been proposed as the origin of FRB, with particular
attention to Soft Gamma Repeaters and giant pulsar pulses.
