  We present the results of an approximately 6,100 square degree 104--196MHz
radio sky survey performed with the Murchison Widefield Array during instrument
commissioning between 2012 September and 2012 December: the Murchison Widefield
Array Commissioning Survey (MWACS). The data were taken as meridian drift scans
with two different 32-antenna sub-arrays that were available during the
commissioning period. The survey covers approximately 20.5 h < Right Ascension
(RA) < 8.5 h, -58 deg < Declination (Dec) < -14 deg over three frequency bands
centred on 119, 150 and 180 MHz, with image resolutions of 6--3 arcmin. The
catalogue has 3-arcmin angular resolution and a typical noise level of 40
mJy/beam, with reduced sensitivity near the field boundaries and bright
sources. We describe the data reduction strategy, based upon mosaiced
snapshots, flux density calibration and source-finding method. We present a
catalogue of flux density and spectral index measurements for 14,110 sources,
extracted from the mosaic, 1,247 of which are sub-components of complexes of
sources.
