  We report the discovery of HATS-17b, the first transiting warm Jupiter of the
HATSouth network. HATS-17b transits its bright (V=12.4) G-type
(M$_{\star}$=1.131 $\pm$ 0.030 M$_{\odot}$,
R$_{\star}$=1.091$^{+0.070}_{-0.046}$ R$_{\star}$) metal-rich ([Fe/H]=+0.3 dex)
host star in a circular orbit with a period of P=16.2546 days. HATS-17b has a
very compact radius of 0.777 $\pm$ 0.056 R$_J$ given its Jupiter-like mass of
1.338 $\pm$ 0.065 M$_J$. Up to 50% of the mass of HATS-17b may be composed of
heavy elements in order to explain its high density with current models of
planetary structure. HATS-17b is the longest period transiting planet
discovered to date by a ground-based photometric survey, and is one of the
brightest transiting warm Jupiter systems known. The brightness of HATS-17b
will allow detailed follow-up observations to characterize the orbital geometry
of the system and the atmosphere of the planet.
