The 7.4 Mw  Manjil–Rudbar earthquake affects northern Iran with a maximum Mercalli intensity of X (Extreme), killing 35,000–50,000, and injuring 60,000–105,000.

The 1990 Manjil–Rudbar earthquake occurred on Thursday, 21 June 1990 at 00:30:14 local time in the Caspian Sea region of northern Iran. The shock had a moment magnitude of 7.4 and a Mercalli Intensity of X (Extreme). Devastation occurred in a 20,000 km² (7,700 sq mi) area, causing extensive damage in several cities. A large aftershock also added to the destruction. Between 35,000 and 50,000 people died in the earthquake; another 60,000–105,000 were injured.

Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the northeast, Afghanistan to the east, Pakistan to the southeast, and the Gulf of Oman and the Persian Gulf to the south. Iran ranks 17th globally in both geographic size and population and is the sixth-largest country in Asia. Iran is divided into five regions with 31 provinces. Tehran is the nation's capital, largest city, and financial center.

The Modified Mercalli intensity scale measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake.