The 2011 Super Outbreak was the largest, costliest, and one of the deadliest tornado outbreaks ever recorded, affecting the Southern, Midwestern, and Northeastern United States and leaving catastrophic destruction in its wake. The event affected Alabama and Mississippi the most severely, but it also produced destructive tornadoes in Arkansas, Georgia, Tennessee and Virginia, and affected many other areas throughout the Southern and Eastern United States. In total, 362 tornadoes were confirmed by NOAA's National Weather Service (NWS) and Government of Canada's Environment Canada in 21 states from Texas to New York to southern Canada. Widespread and destructive tornadoes occurred on each day of the outbreak, with April 27 being the most active day with a record of 218 tornadoes touching down that day from midnight to midnight CDT (0500 – 0500 UTC). Four of the tornadoes were destructive enough to be rated EF5, which is the highest ranking possible on the Enhanced Fujita scale; typically these tornadoes are only recorded about once each year or less.
In total, 348 people were killed as a result of the outbreak, which includes 324 tornado-related deaths across six states and an additional 24 fatalities caused by other thunderstorm-related events such as straight-line winds, hail, flash flooding or lightning. In Alabama alone, 238 tornado-related deaths were confirmed by the Storm Prediction Center (SPC) and the state's Emergency Management Agency.
April 27's 317 fatalities were the most tornado-related fatalities in the United States in a single day since the "Tri-State" outbreak on March 18, 1925 (when at least 747 people were killed). Nearly 500 preliminary local storm reports were received for tornadoes over four days, including 292 in 16 states on April 27 alone. This event was the costliest tornado outbreak and one of the costliest natural disasters in United States history (even after adjustments for inflation), with total damages of approximately $11 billion (2011 USD).