  We report the results of a visual inspection of images of the Rapid ASKAP
Continuum Survey (RACS) in search of extended radio galaxies (ERG) that reach
or exceed linear sizes on the order of one Megaparsec. We searched a contiguous
area of 1059deg$^2$ from RA$_{\rm J}$=20$^h$20$^m$ to 06$^h$20$^m$, and
$-50^{\circ}<\rm{Dec}_J<-40^{\circ}$, which is covered by deep multi-band
optical images of the Dark Energy Survey (DES), and in which previously only
three ERGs larger than 1Mpc had been reported. For over 1800 radio galaxy
candidates inspected, our search in optical and infrared images resulted in
hosts for 1440 ERG, for which spectroscopic and photometric redshifts from
various references were used to convert their largest angular size (LAS) to
projected linear size (LLS). This resulted in 178 newly discovered giant radio
sources (GRS) with LLS$>$1Mpc, of which 18 exceed 2Mpc and the largest one is
3.4Mpc. Their redshifts range from 0.02 to $\sim$2.0, but only 10 of the 178
new GRS have spectroscopic redshifts. For the 146 host galaxies the median
$r$-band magnitude and redshift are 20.9 and 0.64, while for the 32 quasars or
candidates these are 19.7 and 0.75. Merging the six most recent large
compilations of GRS results in 458 GRS larger than 1Mpc, so we were able to
increase this number by $\sim39\%$ to now 636.
