The Greenfield tornado kills 5 and injures 35 across rural Iowa, United States. Wind speeds in excess of 480 kilometres per hour (300 mph) are estimated from measurements for the third time in history.

On the afternoon of May 21, 2024, a violent EF4 tornado tracked across southwestern Iowa, United States, devastating the city of Greenfield. The tornado, known most commonly as the Greenfield tornado, destroyed many buildings and wind turbines across its path that stretched through Page, Taylor, Adams, and Adair counties, while also causing more than $31 million in property damage, killing five people and injuring 35 more. The tornado reached peak intensity within Greenfield, where National Weather Service surveyors denoted maximum wind speeds estimated at 185 mph (298 km/h), or EF4 on the Enhanced Fujita scale. However, estimated winds of 309–318 mph (497–512 km/h) were briefly determined from inside the tornado by a Doppler on Wheels portable radar unit, one of only three times that wind speeds exceeding 300 miles per hour (480 km/h) have been determined in a tornado from radar observations.

Iowa is a state in the upper Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Illinois to the east and southeast, Missouri to the south, Nebraska to the west, South Dakota to the northwest, and Minnesota to the north.

May 21 is the 141st day of the year in the Gregorian calendar; 224 days remain until the end of the year.