Tropical Storm Allison was a tropical storm that devastated southeast Texas in June of the 2001 Atlantic hurricane season. An arguable example of the "brown ocean effect", Allison lasted unusually long for a June storm, remaining tropical or subtropical for 16 days, most of which was when the storm was over land dumping torrential rainfall. The storm developed from a tropical wave in the northern Gulf of Mexico on June 4, 2001, and struck the upper Texas coast shortly thereafter. It drifted northward through the state, turned back to the south, and re-entered the Gulf of Mexico. The storm continued to the east-northeast, made landfall on Louisiana, then moved across the southeast United States and Mid-Atlantic. Allison was the first storm since Tropical Storm Frances in 1998 to strike the northern Texas coastline.

The 2001 Atlantic hurricane season was a fairly active Atlantic hurricane season that produced 17 tropical cyclones, 15 named storms, nine hurricanes, and four major hurricanes. The season officially lasted from June 1, 2001, to November 30, 2001, dates which by convention limit the period of each year when tropical cyclones tend to form in the Atlantic Ocean basin. The season began with Tropical Storm Allison on June 4, and ended with Hurricane Olga, which dissipated on December 6.