  We present pre- and post-explosion observations of the Type II-P supernova
(SN~II-P) 2019mhm located in NGC~6753. Based on optical spectroscopy and
photometry, we show that SN\,2019mhm exhibits broad lines of hydrogen with a
velocity of $-8500\pm200$~km~s$^{-1}$ and a $111\pm2$~day extended plateau in
its luminosity, typical of the Type II-P subclass. We also fit its late-time
bolometric light curve and infer that it initially produced a ${}^{56}$Ni mass
of $1.3 \times 10^{-2}$~M$_{\odot} \pm 5.5 \times 10^{-4}$~$M_\odot$. Using
imaging from the Wide Field Planetary Camera 2 on the {\it Hubble Space
Telescope} obtained 19~years before explosion, we aligned to a post-explosion
Wide Field Camera 3 image and demonstrate that there is no detected counterpart
to the SN to a limit of $>$24.53~mag in F814W, corresponding to an absolute
magnitude limit of $M_{\rm F814W} < -7.7$~mag. Comparing to massive-star
evolutionary tracks, we determine that the progenitor star had a maximum
zero-age main sequence mass $<$17.5~M$_{\odot}$, consistent with other SN~II-P
progenitor stars. SN\,2019mhm can be added to the growing population of
SNe~II-P with both direct constraints on the brightness of their progenitor
stars and well-observed SN properties.
