Huntsville is a city in Madison County, Limestone County, and Morgan County, Alabama. It is the county seat of Madison County. Located in the Appalachian region of northern Alabama, Huntsville is the most populous city in the state.

Huntsville was founded within the Mississippi Territory in 1805 and became an incorporated town in 1811. When Alabama was admitted as a state in 1819, Huntsville was designated for a year as the first capital, before that was moved to more central settlements. The city developed across nearby hills north of the Tennessee River, adding textile mills in the late nineteenth century.

Its major growth has taken place since World War II. During the war, the Army established Redstone Arsenal near here with a chemical weapons plant, and nearby related facilities. After the war, additional research was conducted at Redstone Arsenal on rockets, followed by adaptations for space exploration. NASA's Marshall Space Flight Center, the United States Army Aviation and Missile Command, and most recently the FBI's operational support headquarters all came to be located at nearby Redstone Arsenal. The National Trust for Historic Preservation included Huntsville in its "America's Dozen Distinctive Destinations for 2010" list.

The city's population was 215,006 at the 2020 census, making it Alabama's most populous city. Birmingham had been the largest since the growth of its coal and steel industries earlier in the 20th century. Huntsville is the largest city in the fivecounty HuntsvilleDecaturAlbertville, AL Combined Statistical Area. The Huntsville metropolitan area's population was 491,723 in 2020, making it the second most populous metropolitan area in the state after the Birmingham metropolitan area. Huntsville was named the #1 Best Place to Live in America by U.S. News and World Report in 2022.

Huntsville remains the center for rocketpropulsion research in NASA and the Army. The Marshall Space Flight Center has been designated to develop NASA's Space Launch System (SLS), and the U.S. Army Aviation and Missile Command (AMCOM) is responsible for developing a variety of rocketbased tactical weapons.