  We report the detection of an ultra-bright fast radio burst (FRB) from a
modest, 3.4-day pilot survey with the Australian Square Kilometre Array
Pathfinder. The survey was conducted in a wide-field fly's-eye configuration
using the phased-array-feed technology deployed on the array to instantaneously
observe an effective area of $160$ deg$^2$, and achieve an exposure totaling
$13200$ deg$^2$ hr. We constrain the position of FRB 170107 to a region
$8'\times8'$ in size (90% containment) and its fluence to be $58\pm6$ Jy ms.
The spectrum of the burst shows a sharp cutoff above $1400$ MHz, which could be
either due to scintillation or an intrinsic feature of the burst. This confirms
the existence of an ultra-bright ($>20$ Jy ms) population of FRBs.
