The 1693 earthquake was a disastrous event affecting eastern Sicily, southern Italy, where it caused over 60,000 victims and total destruction of several villages and towns in the districts of Siracusa, Ragusa, and Catania. The earthquake was followed by a tsunami that struck the Ionian coasts of Sicily and the Messina Strait and was probably observed even in the Aeolian Islands. Historical documents on sea waves and flooding, though not abundant, allow us to form a picture of the tsunami first attack and inundation. The first water movement all along the Sicilian coastline was a strong sea withdrawal, followed by a violent sea return and coastal flooding. The main purpose of this research is to put constraints on the focal mechanism of this earthquake on the basis of the available documents on the tsunami (1) by simulating tsunami from different possible sources via numerical modeling based on finite element technique and shallow water approximation and (2) by choosing the source best fitting the tsunami data as the most plausible cause for this tsunami. The relevance of this study should also be evaluated in light of the circumstance that no certain indication on the earthquake fault can be deduced from the available macroseismic data alone. Solving the source problem for this event, one of the largest occurring in southeastern Sicily in historical times, is a significant contribution to understanding the seismotectonic regime of the region and to assessing the related earthquake and tsunami hazard/risk with implications on mitigation policies. ¿ 1998 American Geophysical Union