The 1991 Racha earthquake occurred in the province of Racha, Georgia, at 9:12 UTC on 29 April. Centered on the districts of Oni and Ambrolauri on the southern foothills of the Greater Caucasus mountains, it killed 270, left approximately 100,000 homeless and caused severe damage, including to several medieval monuments. It had a magnitude of 7.0 and was the most powerful earthquake recorded in the Caucasus.
Georgia lies between the two mountain chains of the Greater Caucasus in the north and the Lesser Caucasus in the south. These two sets of mountains have both resulted from the continuing effects of the collision between the Arabian Plate and the Eurasian Plate. The Greater Caucasus consists of a southward-directed fold and thrust belt that has been active since the Oligocene. Racha lies close to the southern margin of this thrust belt and the earthquake is interpreted to be caused by rupture of the active thrust front.