A single isolated electron in a Penning trap yields a new measurement of the electron magnetic moment g/2 = 1.001 159 652 180 59 (13). Combined with the Standard Model calculation, this yields an independent determination of the fine structure constant α−1 = 137.035 999 166 (16). Comparison of the measured g-factor and the predicted g-factor using an independent measurement of the fine structure constant yields the most stringent test of the Standard Model.