View source for 2021 Western Kentucky tornado (Shark's Reanalysis)

{{Infobox weather event/EF
|name=2021 Western Kentucky tornado
|multiple image={{multiple image
| border = infobox
| perrow = 1/2
| total_width = 300
| image1 = 2021 Mayfield, Kentucky, tornado CROPPED.png
| image2 = Radar of the Quad-State Supercell prior to impacting Mayfield, Kentucky.png
| image3 = SPC Mesoscale Discussion 1999.jpg
| image4 = Bremen EF5 Damage.jpg
| image5 = Ariel Damage in Mayfield.jpg
}}
|image caption={{Unbulleted list|'''Clockwise from top:''' The EF5 tornado illuminated by lightning near Bremen in Muhlenberg County; Storm Prediction Center mesoscale discussion of the tornado as it was ongoing; low-end EF5 damage to a home in Bremen; a radar scan of the supercell showing the tornado as it struck Mayfield}}
|formed=December 10, 2021, 8:54 p.m. CST (UTC−06:00)
|dissipated=December 10, 2021, 11:48 p.m. CST (UTC−06:00)
|duration=2 hours, 54 minutes
|maxwidth=2600
|pathlength=165.6
|preliminary-rating=EF5
|highest winds=
|fatalities=57 (+1 indirect)
|injuries=519
|affected=Obion County, Tennessee and Western Kentucky, United States
|tornado outbreak=tornado outbreak of December 10–11, 2021
|tornado year=tornado outbreaks of 2021
}}

'''Reanalysis In Progress.'''

During the late evening hours of Friday, December 10, 2021, a massive and devastating EF5 tornado, sometimes referred to as the '''Western Kentucky tornado''', '''Mayfield tornado''', or '''The Beast''', tracked a significant distance across Western Kentucky, United States, producing severe-to-catastrophic damage in numerous towns, including Mayfield, Princeton, Dawson Springs, and Bremen. This tornado was the second significant tornado in an exceedingly long-tracked tornado family; it began just inside northern Obion County, Tennessee, a few miles after another long-tracked tornado that traveled through northeast Arkansas, the Missouri Bootheel, and northwest Tennessee and dissipated in western Obion County. After crossing into Kentucky, the tornado moved through eleven counties of the Jackson Purchase and Western Coal Field regions, at times becoming wrapped in rain during its almost three-hour lifespan that covered {{convert|165.6|mi|km}}. It was the deadliest and longest-tracked tornado in an outbreak that produced numerous, strong tornadoes in several states; this tornado caused 57 deaths.

Early estimates suggested the tornado family, which some media outlets described as a "Quad-State tornado" due to the storm's long track and similarity to the {{convert|219|mi|km|adj=on}} Tri-State tornado of 1925, might have traveled {{convert|250|mi|km}} on the ground, making it the longest-tracked tornado in history. Storm surveys found the majority of the storm's path consisted of two separate EF4 tornadoes, and three weaker, short-lived tornadoes in between them in northwestern Obion County, Tennessee. The parent supercell that produced the two EF4 tornadoes, and eleven tornadoes in total, later became known as the Quad-State supercell.

After the tornado, a state of emergency and a federal disaster were declared by Governor Andy Beshear and President Joe Biden on December 11. The death toll of 57 was the highest from a tornado in the month of December in U.S. history, while also being the deadliest tornado since 2011. Some of the worst damage occurred in Mayfield and was considered by some National Weather Service (NWS) analysts in a case study as bordering on EF5 intensity, prompting discussion on the intensity of high-end tornadoes and damage requirements.

Multiple workers at the Mayfield Consumer Products candle factory that was destroyed with multiple casualties alleged that supervisors told them they would be fired if they left their shifts early ahead of the storm's direct hit on the city. Company spokespeople have denied the allegations. On December 17, it was reported that multiple workers (only one was named due to fear of reprisal) filed a class-action lawsuit against the company. The lawsuit alleged that the company had up to three and a half hours to allow employees to leave before the tornado hit the factory and showed a flagrant indifference to the rights of the workers.

In the years following the December 10, 2021 Western Kentucky tornado, debate persisted among meteorologists and storm researchers regarding the tornado’s official intensity, particularly in light of later rating decisions on other significant events. Some independent analysts and damage surveyors argued that certain damage indicators—such as complete destruction of well-built homes and extensive structural failures—might be consistent with EF5-level winds, even though the National Weather Service (NWS) ultimately rated the tornado as a high-end EF4.

The topic of tornado rating and damage interpretation gained additional attention following the June 20, 2025 Enderlin, North Dakota tornado, which was initially rated EF3 but was upgraded to EF5 in October 2025 after further study of damage indicators such as train car derailment and severe structural effects. This upgrade — the first EF5 rating in the United States since 2013 — sparked broader discussion about methodologies used in Enhanced Fujita (EF) scale assessments and the thresholds for categorizing the most violent tornadoes.

Some researchers and observers referenced the 2025 Enderlin reclassification in debates over whether the Western Kentucky tornado merited reconsideration, highlighting challenges in comparing damage across different environments and construction practices and in applying the EF scale consistently. These conversations have contributed to ongoing professional discourse about potential refinements to tornado rating practices and the complexities inherent in extreme wind damage analysis.