  We present a comprehensive analysis of the 0.3--5\,$\mu$m transit spectrum
for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with
Hubble STIS and WFC3 as part of the Hubble Panchromatic Comparative Exoplanet
Treasury (PanCET) program, and we combine those data with warm \textit{Spitzer}
transit observations. We extract transit depths from each of the data sets,
presenting the STIS transit spectrum (0.29--0.93\,$\mu$m) for the first time.
We retrieve the transit spectrum both with a free-chemistry retrieval suite
(AURA) and a complementary chemical equilibrium retrieval suite (PLATON) to
constrain the atmospheric properties at the day-night terminator. Both methods
provide an excellent fit to the observed spectrum. Both AURA and PLATON
retrieve a metal-rich atmosphere for almost all model assumptions (most likely
O/H ratio of $\log_{10}{Z/Z_{\odot}} = 1.46^{+0.53}_{-0.68}$ and
$\log_{10}{Z/Z_{\odot}} = 2.33^{+0.23}_{-0.25}$, respectively); this is driven
by a 4.9-$\sigma$ detection of H$_2$O as well as evidence of gas absorption in
the optical ($>$2.7-$\sigma$ detection) due to Na, AlO and/or VO/TiO, though no
individual species is strongly detected. Both retrievals determine the transit
spectrum to be consistent with a clear atmosphere, with no evidence of haze or
high-altitude clouds. Interior modeling constraints on the maximum atmospheric
metallicity ($\log_{10}{Z/Z_{\odot}} < 1.7$) favor the AURA results. The
inferred elemental oxygen abundance suggests that HAT-P-41b has one of the most
metal-rich atmospheres of any hot Jupiters known to date. Overall, the inferred
high metallicity and high inflation make HAT-P-41b an interesting test case for
planet formation theories.
