  We report on the first observation of a radio-quiet Active Galactic Nucleus
(AGN) using polarized X-rays: the Seyfert 1.9 galaxy MCG-05-23-16. This source
was pointed with the Imaging X-ray Polarimetry Explorer (IXPE) starting on May
14, 2022 for a net observing time of 486 ks, simultaneously with XMM-Newton (58
ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at the
99% c.l.) is derived in the 2-8 keV energy range, where emission is dominated
by the primary component ascribed to the hot corona. The broad-band spectrum,
inferred from a simultaneous fit to the IXPE, NuSTAR, and XMM-Newton data, is
well reproduced by a power law with photon index $\Gamma=1.85\pm0.01$ and a
high-energy cutoff $E_{\rm C}=120\pm15$ keV. A comparison with Monte Carlo
simulations shows that a lamp-post and a conical geometry of the corona are
consistent with the observed upper limit, a slab geometry is allowed only if
the inclination angle of the system is less than 50$^{\circ}$.
