  We present a sample of nine Fast Radio Bursts (FRBs) from which we derive
magnetic field strengths of the host galaxies represented by normal, $z<0.5$
star-forming galaxies with stellar masses $M_* \approx 10^8 -10^{10.5}
M_\odot$. We find no correlation between the FRB rotation measure(RM) and
redshift which indicates that the RM values are due mostly to the FRB host
contribution. This assertion is further supported by strong correlations
(Spearman test probabilities $P_S \simeq 0.05$) found between RM and the
estimated host dispersion measure ($DM_{Host}$) and host-normalized
galacto-centric offset (Spearman $r_S$ values equal to 0.64 and -0.52). For
these nine galaxies, we estimate their magnetic field strengths projected along
the sightline $B$ finding a low median value of $0.5 \mu G$. This implies the
magnetic fields of our sample of hosts are weaker than those characteristic of
the Solar neighborhood ($\approx 6 \mu G$), but relatively consistent with a
lower limit on observed range of $2-10 \mu G$ for star-forming, disk galaxies,
especially as we consider reversals in the B-field, and that we are only
probing $B_{\parallel}$. We compare to RMs from simulated galaxies of the
Auriga project -- magneto-hydrodynamic cosmological zoom simulations - and find
that the simulations predict the observed values to within the $95\%$ CI.
Upcoming FRB surveys will provide hundreds of new FRBs with high-precision
localizations, rotation measures, and imaging follow-up to support further
investigation on the magnetic fields of a diverse population of $z<1$ galaxies.
