Synchrotron emission from a population of ultra-relativistic electrons in the inner Galaxy has been observed by the Wilkinson Microwave Anisotropy Probe (WMAP). After careful modeling of the microwave foreground signals from Galactic interstellar medium a residual microwave signal is present within 10-20 degrees of the Galactic center, uncorrelated with any known foreground template. The most likely explanation for this mysterious component is synchrotron emission from an unusually hot electron energy distribution. The source of these electrons is still uncertain, but the spatial distribution, inferred energy spectrum, and total number are consistent with their being positron-electron pairs produced by WIMP annihilation.