New low frequency 74 and 330 MHz observations of the Galactic center (GC) region reveal the presence of a large-scale (6\arcdeg* 2\arcdeg) diffuse source of nonthermal synchrotron emission. A minimum energy analysis of this emission yields a total energy of ( phi 4/7f3/7)* 1052 ergs and a magnetic field strength of 6( phi /f)2/7 mu G , (where phi is the proton to electron energy ratio and f is the filling factor of the synchrotron emitting gas). The equipartition particle energy density is 1.2( phi /f)2/7 \evcm , a value consistent with cosmic ray data. However, the derived magnetic field is several orders of magnitude below the 1 mG field commonly invoked for the GC. The shorter electron radiation lifetimes in such a strong field requires that energy be resupplied to the source at an implausibly high rate. Furthermore, a strong magnetic field implies an abnormally low GC cosmic ray energy density. We conclude that the mean magnetic field in the GC region must be weak, of order 10 mu G (at least on size scales > 125'').