The pure rotational spectrum of the MgF radical in its ground electronic state (X(2) Sigma(+)) has been recorded using millimeter/submillimeter direct absorption techniques. Transitions arising from the v=0, 1, 2, and 3 vibrational modes of the main magnesium isotopic species, (MgF)-Mg-24, have been observed. In addition, spectra of the isotopomers (MgF)-Mg-26 and (MgF)-Mg-25 in the natural abundances of magnesium have been detected. Rotational and fine structure constants have been determined for these species, as well as hyperfine parameters for the fluorine nucleus (I=1/2). For (MgF)-Mg-25, the hyperfine structure was also resolved arising from the magnesium nucleus, which has I=5/2, yielding the Mg-25 hyperfine and quadrupole constants. Comparison of these hyperfine parameters with those of the heavier alkaline-earth manofluorides and the free Mg-25(+) atom suggests that there is an increase in covalent bonding in MgF vs its heavier fluoride counterparts. This behavior is also apparent in the hybridization of the wave function of the unpaired electron in MgF, which appears to consist of almost equal s and p character.