  We confirm the planetary nature of TOI-532b, using a combination of precise
near-infrared radial velocities with the Habitable-zone Planet Finder, TESS
light curves, ground based photometric follow-up, and high-contrast imaging.
TOI-532 is a faint (J$\sim 11.5$) metal-rich M dwarf with Teff = $3957\pm69$ K
and [Fe/H] = $0.38\pm0.04$; it hosts a transiting gaseous planet with a period
of $\sim 2.3$ days. Joint fitting of the radial velocities with the TESS and
ground-based transits reveal a planet with radius of $5.82\pm0.19$
R$_{\oplus}$, and a mass of $61.5_{-9.3}^{+9.7}$ M$_{\oplus}$. TOI-532b is the
largest and most massive super Neptune detected around an M dwarf with both
mass and radius measurements, and it bridges the gap between the Neptune-sized
planets and the heavier Jovian planets known to orbit M dwarfs. It also follows
the previously noted trend between gas giants and host star metallicity for M
dwarf planets. In addition, it is situated at the edge of the Neptune desert in
the Radius--Insolation plane, helping place constraints on the mechanisms
responsible for sculpting this region of planetary parameter space.
