In this paper, we propose a new method for locating lightning discharges. The proposed method is based on the time reversal technique introduced for acoustics in the early 1990s. By analogy to the derivations in acoustics, equations for the focusing of electromagnetic fields back to the source by time reversal are derived. We show that the wavefronts generated by back-propagating the time-reversed fields will add up in phase at the lightning strike location. Based on this observation, we present an algorithm to locate lightning discharges which requires at least three field sensors. The algorithm is illustrated and shown to be very efficient using numerically-generated fields for different cases and considering different numbers of sensors.