  We present WALLABY pilot data release 1, the first public release of HI pilot
survey data from the Wide-field ASKAP L-band Legacy All-sky Blind Survey
(WALLABY) on the Australian Square Kilometre Array Pathfinder. Phase 1 of the
WALLABY pilot survey targeted three $60~{\rm deg}^2$ regions on the sky in the
direction of the Hydra and Norma galaxy clusters and the NGC 4636 galaxy group,
covering the redshift range of z < 0.08. The source catalogue, images and
spectra of nearly 600 extragalactic HI detections and kinematic models for 109
spatially resolved galaxies are available. As the pilot survey targeted regions
containing nearby group and cluster environments, the median redshift of the
sample of z ~ 0.014 is relatively low compared to the full WALLABY survey. The
median galaxy HI mass is $2.3 \times 10^{9}~M_{\odot}$. The target noise level
of 1.6 mJy per $30''$ beam and 18.5 kHz channel translates into a $5\sigma$ HI
mass sensitivity for point sources of about $5.2 \times 10^{8} \, (D_{\rm L} /
\mathrm{100~Mpc})^{2} \, M_{\odot}$ across 50 spectral channels (~200 km/s) and
a $5\sigma$ HI column density sensitivity of about $8.6 \times 10^{19} \, (1 +
z)^{4}~\mathrm{cm}^{-2}$ across 5 channels (~20 km/s) for emission filling the
$30''$ beam. As expected for a pilot survey, several technical issues and
artefacts are still affecting the data quality. Most notably, there are
systematic flux errors of up to several 10% caused by uncertainties about the
exact size and shape of each of the primary beams as well as the presence of
sidelobes due to the finite deconvolution threshold. In addition, artefacts
such as residual continuum emission and bandpass ripples have affected some of
the data. The pilot survey has been highly successful in uncovering such
technical problems, most of which are expected to be addressed and rectified
before the start of the full WALLABY survey.
