Tornadoes kill dozens and sometimes hundreds of people every year in the United States. Warning systems have improved dramatically, however, so some of the deadliest tornadoes were recorded many decades ago. In some cases, a single tornado caused hundreds of deaths. Following are the 10 deadliest on record, based on data from the Federal Emergency Management Agency (FEMA). Strengths are measured from F1 to F5 (strongest) on the Fujita scale.

Robert Pershing Wadlow (February 22, 1918 – July 15, 1940) was a man who, to this day, is the tallest person in medical history for whom there is irrefutable evidence. He is often known as the "Alton Giant" because of his Alton, Illinois hometown. Wadlow was noted for having the largest and broadest hands ever in recorded history being capable to hide a 2-liter bottle of soda in them easily.

Wadlow reached 8 feet 11.1 inches (2.72 m) in height and weighed 490 pounds (220 kg) at his death. His great size and his continued growth in adulthood was due to hypertrophy of his pituitary gland which results in an abnormally high level of human growth hormone. He showed no indication of an end to his growth even at the time of his death.