The 1138 Aleppo earthquake was among the deadliest earthquakes in history. Its name was taken from the city of Aleppo, in northern Syria, where the most casualties were sustained. The earthquake also caused damage and chaos to many other places in the area around Aleppo. The quake occurred on 11 October 1138 and was preceded by a smaller quake on the 10th. It is frequently listed as the third deadliest earthquake in history, following on from the Shensi and Tangshan earthquakes in China. However, the figure of 230,000 deaths reported by Ibn Taghribirdi in the fifteenth century is most likely based on a historical conflation of this earthquake with earthquakes in November 1137 on the Jazira plain and the large seismic event of 30 September 1139 in the Transcaucasian city of Ganja.

Aleppo is a city in Syria, which serves as the capital of the Aleppo Governorate, the most populous governorate of Syria. With an estimated population of 2,098,000 residents as of 2021, it was Syria's largest city until its population was surpassed by Damascus, the capital of Syria, the largest in Syria's northern governorates and also one of the largest cities in the Levant region.