  Since first noticed by Shapley in 1939, a faint object coincident with the
Fornax dwarf spheroidal has long been discussed as a possible sixth globular
cluster system. However, debate has continued over whether this overdensity is
a statistical artifact or a blended galaxy group. In this Letter we
demonstrate, using deep DECam imaging data, that this object is well resolved
into stars and is a bona fide star cluster. The stellar overdensity of this
cluster is statistically significant at the level of ~ 6 - 6.7 sigma in several
different photometric catalogs including Gaia. Therefore, it is highly unlikely
to be caused by random fluctuation. We show that Fornax 6 is a star cluster
with a peculiarly low surface brightness and irregular shape, which may
indicate a strong tidal influence from its host galaxy. The Hess diagram of
Fornax 6 is largely consistent with that of Fornax field stars, but it appears
to be slightly bluer. However, it is still likely more metal-rich than most of
the globular clusters in the system. Faint clusters like Fornax 6 that orbit
and potentially get disrupted in the centers of dwarf galaxies can prove
crucial for constraining the dark matter distribution in Milky Way satellites.
