  The Variables and Slow Transients Survey (VAST) on the Australian Square
Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and
transient radio sources on timescales from 5 seconds to $\sim 5$ years. In this
paper, we present the survey description, observation strategy and initial
results from the VAST Phase I Pilot Survey. This pilot survey consists of $\sim
162$ hours of observations conducted at a central frequency of 888~MHz between
2019 August and 2020 August, with a typical rms sensitivity of
0.24~mJy~beam$^{-1}$ and angular resolution of $12-20$ arcseconds. There are
113 fields, \red{each of which was observed for 12 minutes integration time},
with between 5 and 13 repeats, with cadences between 1 day and 8 months. The
total area of the pilot survey footprint is 5\,131 square degrees, covering six
distinct regions of the sky. An initial search of two of these regions,
totalling 1\,646 square degrees, revealed 28 highly variable and/or transient
sources. Seven of these are known pulsars, including the millisecond pulsar
J2039--5617. Another seven are stars, four of which have no previously reported
radio detection (SCR~J0533--4257, LEHPM~2-783, UCAC3~89--412162 and 2MASS
J22414436--6119311). Of the remaining 14 sources, two are active galactic
nuclei, six are associated with galaxies and the other six have no
multiwavelength counterparts and are yet to be identified.

High Energy Astrophysical Phenomena