Avatar: The Last Airbender (Avatar: The Legend of Aang in some regions) is an American animated television series created by Michael Dante DiMartino and Bryan Konietzko, with Aaron Ehasz as head writer. It aired on Nickelodeon for three seasons, from February 2005 to July 2008. Avatar is set in an Asiatic-like world in which some people can manipulate one of the four elements—water, earth, fire, or air—with telekinetic variants of the Chinese martial arts known as "bending". The only individual who can bend all four elements, the "Avatar", is responsible for maintaining harmony between the world's four nations, and serves as the bridge between the spirit world and the physical world. The show is presented in a style that combines anime with American cartoons, and relies on the imagery of mainly East Asian culture, with some South Asian, New World, and Inuit and Sireniki influences.

The series is centered around the journey of 12-year-old Aang, the current Avatar and last survivor of his nation, the Air Nomads, along with his friends Sokka, Katara, and later Toph, as they strive to end the Fire Nation's war against the other nations of the world. It also follows the story of Zuko—the exiled prince of the Fire Nation, seeking to restore his lost honor by capturing Aang, accompanied by his wise uncle Iroh—and later, that of his ambitious sister Azula.

Avatar: The Last Airbender was commercially successful and acclaimed by audiences and critics, who praised its art direction, soundtrack, cultural references, humor, characters, and themes. These include concepts rarely touched on in youth entertainment, such as war, genocide, imperialism, totalitarianism, and free choice. It won five Annie Awards, a Genesis Award, a Primetime Emmy Award, a Kids' Choice Award, and a Peabody Award. A number of critics have referred to Avatar as one of the best (animated) television series of all time.

The extended Avatar franchise includes an ongoing comics series, a prequel novel series, an animated sequel series, and a live-action film, as well as an upcoming live-action remake of the show produced for Netflix. The complete series was released on Blu-ray in June 2018 in honor of the 10th anniversary of its finale, and was made available to stream on Netflix in the United States in May 2020, and on CBS All Access in June 2020.