A 6.8 Mw earthquake strikes the Uttarkashi region of India, killing more than 1,000 people.

The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment. M_w  was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude/Richter scale (M_L ) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales. Despite the difference, news media often use the term "Richter scale" when referring to the moment magnitude scale.

The 1991 Uttarkashi earthquake occurred at 02:53:16 Indian Standard Time (UTC+05:30) on 20 October with a moment magnitude of 6.8 and a maximum Mercalli intensity of IX (Violent). This thrust event was instrumentally recorded and occurred along the Main Central Thrust in the Uttarkashi and Gharwal regions of the Indian state of Uttarakhand. High intensity shaking resulted in the deaths of at least 768 people and the destruction of thousands of homes.

Uttarkashi District is a district of Garhwal division of the Uttarakhand state in northern India, and has its headquarters at Uttarkashi city. It has six Tehsils namely Barkot, Dunda, Bhatwadi, Chinyalisaur, Purola and Mori.