Toxicity is the second studio album by Armenian-American heavy metal band System of a Down, released on September 4, 2001, through American Recordings and Columbia Records. Expanding on their 1998 eponymous debut, it incorporated more melody, harmonies, and singing than the band's aforementioned album. Categorized primarily as alternative metal and nu metal, Toxicity features elements of multiple genres including folk, progressive rock, jazz, Armenian music and Greek music, including prominent use of instruments such as the sitar, banjo, keyboards, and piano. It contains a wide array of political and non-political themes, such as mass incarceration, the CIA, the environment, police brutality, drug addiction, scientific reductionism, and groupies.
 
Toxicity was recorded at Cello Studios in Hollywood, California. Over thirty songs were recorded, but the band narrowed the number of songs on the album to fourteen. The album peaked at number one on both the Billboard 200 and the Canadian Albums Chart, sold 220,000 copies in its first week of release, was certified triple-platinum by the Recording Industry Association of America in November 2002, and has sold at least 2,700,000 copies in the United States. All of Toxicity's singles reached the Billboard Hot 100. The final single, "Aerials", went to number one on both the Mainstream Rock Tracks and the Modern Rock Tracks charts. Toxicity received mainly positive ratings and reviews from critics, among them perfect ratings from AllMusic, Kerrang!, and Blabbermouth.net. Many critics praised the album's sound and innovation.