This article presents a general method of estimating earthquake magnitude using regional phase amplitudes, called regional M0 or regional Mw. Conceptually, this method uses an earthquake source model along with an attenuation model and geometrical spreading that accounts for the propagation to utilize regional phase amplitudes of any phase and frequency. Amplitudes are corrected to yield a source term from which one can estimate the seismic moment. Moment magnitudes can then be reliably determined with sets of observed phase amplitudes rather than predetermined ones and afterward averaged to robustly determine this parameter. We first examine in detail two events to demonstrate the methodology. We then look at various ensembles of phases and frequencies and compare results to existing regional methods. We find regional M0 to be a stable estimator of earthquake size that has several advantages over other methods. Because of its versatility, it is applicable to many more events, particularly smaller events. We make moment estimates for earthquakes ranging from magnitude 2 to as large as 7. Even with diverse input amplitude sources, we find magnitude estimates with this method to be more robust than typical magnitudes and existing regional methods, and the magnitude estimates might be tuned further to improve upon them. The method yields a more meaningful quantity of seismic moment, which can be recast as Mw. Lastly, it is applied here to the Middle East region using an existing calibration model, but it would be easy to transport to any region with suitable attenuation calibration.