A violent earthquake struck the Caucasus near Ganja, killing up to an estimated 300,000 people.

The 1139 Ganja earthquake was one of the worst seismic events in history. It affected the Seljuk Empire and the Kingdom of Georgia, in modern-day Azerbaijan and Georgia. The earthquake had an estimated magnitude of 7.7 M_LH, 7.5 M_s and 7.0–7.3 M_w. A disputed death toll of 230,000–300,000 resulted from this event, making it one of the deadliest earthquakes ever recorded.

The Caucasus or Caucasia is a region spanning Eastern Europe and Western Asia. It is situated between the Black Sea and the Caspian Sea, comprising parts of Southern Russia, Georgia, Armenia, and Azerbaijan. The Caucasus Mountains, including the Greater Caucasus range, have conventionally been considered as a natural barrier between Europe and Asia, bisecting the Eurasian landmass.

Ganja is Azerbaijan's third largest city, with a population of around 335,600. The city has been a historic and cultural center throughout most of its existence. It was the capital of the Ganja Khanate until 1804; after Qajar Iran ceded it to the Russian Empire following the Treaty of Gulistan in 1813, it became part of the administrative divisions of the Georgia Governorate, Georgia-Imeretia Governorate, Tiflis Governorate, and Elizavetpol Governorate. Following the dissolution of the Russian Empire and the Transcaucasian Democratic Federative Republic, it became a part of the Azerbaijan Democratic Republic, followed by Azerbaijan SSR, and, since 1991, the Republic of Azerbaijan.