  We report on the discovery of a significant and compact over-density of old
and metal-poor stars in the KiDS survey (data release 4). The discovery is
confirmed by deeper HSC-SSC data revealing the old Main Sequence Turn-Off of a
stellar system located at a distance from the sun of
$D_{\sun}=145^{+14}_{-13}$~kpc in the direction of the Sextans constellation.
The system has absolute integrated magnitude ($M_V=-3.9^{+0.4}_{-0.3}$),
half-light radius ($r_h=193^{+61}_{-46}$~pc), and ellipticity
($e=0.46^{+0.11}_{-0.15}$) typical of Ultra Faint Dwarf galaxies (UFDs). The
central surface brightness is near the lower limits of known local dwarf
galaxies of similar integrated luminosity, as expected for stellar systems that
escaped detection until now. The distance of the newly found system suggests
that it is likely a satellite of our own Milky Way, consequently, we
tentatively baptise it Sextans~II (KiDS-UFD-1).
