The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of the 21 cm radio emission from neutral hydrogen (HI) in the Local Universe. It is hosted by the Australian Square Kilometer Array Pathfinder (ASKAP) telescope, WALLABY will survey three-quarters of the sky over a Declination range −90° to +30° to a redshift of 0.26. It will have a angular resolution of 30 arcsec and a sensitivity of 1.6 mJy/beam in each 4 km/s channel. WALLABY is expected to detect about 500,000 galaxies with a mean redshift of 0.05, at a mean distance of about 200 Mpc. The scientific goals of WALLABY include: