A major earthquake strikes Beirut, triggering a devastating tsunami that affects the coastal towns of Byzantine Phoenicia, causing thousands of deaths.

The 551 Beirut earthquake occurred on 9 July with an estimated magnitude of about 7.5 on the moment magnitude scale and a maximum felt intensity of X (Extreme) on the Mercalli intensity scale. It triggered a devastating tsunami which affected the coastal towns of Byzantine Phoenicia, causing great destruction and sinking many ships. Overall large numbers of people were reported killed, with one estimate of 30,000 by the anonymous pilgrim of Piacenza for Berytus alone.

Phoenicia under Roman rule describes the Phoenician city states ruled by Rome from 64 BCE to the Muslim conquests of the 7th century. The area around Berytus was the only Latin speaking and Romanized part of Aramaic-speaking Phoenicia.

July 9 is the 190th day of the year in the Gregorian calendar; 175 days remain until the end of the year.