The Massacre of Thessalonica (Thessaloniki) in Greece was a massacre of local civilians by Roman troops. The best estimate of the date is 390. The most probable cause was the murder of a Roman official in an urban riot; the riot was likely caused by the arrest of a local charioteer for sexual assault, the people's demand for his release, and the official's refusal, although, this is found in only one source. In response, imperial soldiers killed a large number of citizens when they were assembled in Thessalonica's hippodrome.