  We report the discovery of a cold stream near the southern Galactic pole
(dubbed as SGP-S) detected in $Gaia$ Early Data Release 3. The stream is at a
heliocentric distance of $\sim$ 9.5 kpc and spans nearly 58$^\circ$ by
0.6$^\circ$ on sky. The colour-magnitude diagram of SGP-S indicates an old and
metal-poor (age $\sim$ 12 Gyr, [M/H] $\sim$ -2.0 dex) stellar population. The
stream's surface brightness reaches an exceedingly low level of $\Sigma_G
\simeq$ 36.2 mag arcsec$^{-2}$. Neither extant globular clusters nor other
known streams are associated with SGP-S.
