  We report measurements of the isotope shifts of the $3d^64s^2 a ^5D_4 -
3d^64s4p z ^5F_5^o$ Fe I resonance line at 372 nm between all four stable
isotopes $^{54}$Fe, $^{56}$Fe, $^{57}$Fe, and $^{58}$Fe, as well as the
complete hyperfine structure of that line for $^{57}$Fe, the only stable
isotope having a non-zero nuclear spin. The field and specific mass shift
coefficients of the transition have been derived from the data, as well as the
experimental value for the hyperfine structure magnetic dipole coupling
constant $A$ of the excited state of the transition in $^{57}$Fe: $A(3d^64s4p z
^5F_5^o) = 81.69(86)$ MHz. The measurements were done by means of Doppler-free
laser saturated-absorption spectroscopy in a Fe-Ar hollow cathode using both
natural and enriched iron samples. The measured isotope shifts and hyperfine
constants are reported with uncertainties at the percent level.
