"Toxic" is a song by American singer Britney Spears for her fourth studio album, In the Zone (2003). It was written and produced by Bloodshy & Avant, with additional writing from Cathy Dennis and Henrik Jonback. Released as the second single from In the Zone, the song was initially offered to Kylie Minogue for her album Body Language, but she turned it down. After trying to choose between "(I Got That) Boom Boom" and "Outrageous" to be the second single, Spears selected "Toxic" instead. A dance-pop and techno-pop song with elements of bhangra music, "Toxic" features varied instrumentation, such as drums, synthesizers and surf guitar. It is accompanied by high-pitched Bollywood strings, sampled from Lata Mangeshkar and S. P. Balasubrahmanyam's "Tere Mere Beech Mein" (1981), and breathy vocals. Its lyrics draw an extended metaphor of a lover as a dangerous yet addictive drug.
"Toxic" received universal acclaim from music critics, who praised its hook and chorus while some deeming it the strongest track on the album. It won Best Dance Recording at the 47th Annual Grammy Awards, marking the first Grammy win of Spears' career. The song was a worldwide success, topping the charts in ten countries including Australia, Canada, Hungary, Ireland, Norway and the United Kingdom, and reached the top five in 15 countries. In the United States, it became her fourth top-ten single, peaking at number nine. The accompanying music video for "Toxic" was directed by Joseph Kahn and features references to Blade Runner, The Seven Year Itch and John Woo films. It features Spears as a secret agent in search of a vial of green liquid. After she steals it, she enters an apartment and poisons her boyfriend. The video also includes interspersed scenes of Spears naked with diamonds on her body. After Justin Timberlake and Janet Jackson's Super Bowl incident, the video was considered too racy for MTV and was moved to late-night programming.
Spears has performed "Toxic" in live appearances, including the 2004 NRJ Music Awards and three of her concert tours. It was the opening number of The Onyx Hotel Tour (2004), where she sang atop a bus wearing a black catsuit; Spears also performed remixed versions of "Toxic" at The Circus Starring Britney Spears (2009), the Femme Fatale Tour (2011) and Britney: Piece of Me (2013). "Toxic" has been covered by artists such as Mark Ronson, A Static Lullaby, Reece Mastin and Ingrid Michaelson, and in the TV series Glee. It has also appeared in films such as Knocked Up, You Again and Pitch Perfect 3, and TV series Doctor Who and Chuck. "Toxic" has been included in lists by Pitchfork, NME and Rolling Stone as one of the best songs of the 2000s. In 2021, the song was ranked at number 114 on the list of Rolling Stone's 500 Greatest Songs of All Time.