  We report the discovery of an ultra-faint star cluster in the constellation
of Centaurus. This new stellar system, Kim 3, features a half light radius of
$r_{h}=2.29^{+1.28}_{-0.52}$ pc and a total luminosity of $M_{V}=+0.7\pm0.3$.
Approximately 26 stars are identified as candidate member stars down to four
magnitudes below the main-sequence turn-off, which makes Kim 3 the least
luminous star cluster known to date. The compact physical size and extreme low
luminosity place it close to faint star clusters in the size-luminosity plane.
The stellar population of Kim 3 appears to be relatively young
($9.5^{+3.0}_{-1.7}$ Gyr) and metal-poor ([Fe/H]$=-1.6^{+0.45}_{-0.30}$) at a
heliocentric distance of $15.14^{+1.00}_{-0.28}$ kpc. The cluster lacks a
well-defined center and a small but prominent group of stars consistent with
the Kim 3 isochrone is present approximately 9.7 pc in projection south of the
cluster center. Both are signs of the cluster being in the final stage of tidal
disruption.
