The 856 Damghan Earthquake, or the 856 Qumis earthquake, occurs on December 22, 856.

The earthquake has an estimated magnitude of 7.9, and a maximum intensity of X (intense) on the Mercalli intensity scale.

The meizoseismal area (area of maximum damage) extends for about three hundred and fifty kilometers (two hundred and twenty miles) along the southern edge of the eastern Alborz Mountains of present-day Iran, including parts of Tabaristan and Gorgan.

The earthquake's epicenter is estimated to be close to the city of Damghan, which is at this time the capital of the Persian province of Qumis.

It causes approximately two hundred thousand deaths and is listed by the USGS as the sixth deadliest earthquake in recorded history.