"Toxic" is a song by American recording artist Britney Spears from her fourth album, In the Zone. It was released on January 12, 2004, by Jive Records as the second single from the album. Co-written and produced by Bloodshy & Avant, the song was initially offered to Kylie Minogue. After trying to choose between "(I Got That) Boom Boom" and "Outrageous" to be the second single from In the Zone, Spears selected "Toxic" instead. A dance-pop song with influences of electropop and bhangra music, "Toxic" features varied instrumentation, such as drums, synthesizers and surf guitar. It is accompanied by high-pitched strings and breathy vocals. Its lyrics refer to being addicted to a lover. The song was well received by critics, who deemed it as the strongest track of In the Zone, while praising its hook and chorus.
"Toxic" attained worldwide success, reaching the top-five in fifteen countries, while topping the charts in Australia, Canada, Hungary, Norway and the United Kingdom. In the United States, it became her first single to peak inside the top ten in almost four years. The accompanying music video for the song was directed by Joseph Kahn and features references to Blade Runner, The Seven Year Itch and the films of John Woo. It portrays Spears as a secret agent in the search of a vial of green liquid. After she steals it, she enters an apartment and poisons her unfaithful boyfriend. The video also includes interspersed scenes of Spears naked with diamonds over her body. After Janet Jackson's Superbowl incident, the video was considered too racy for MTV and was moved to late-night programming. "Toxic" is known for showing Spears for the first time as a confident adult woman, comfortable with her own sexuality.
Spears has performed "Toxic" in a number of live appearances, including the 2004 NRJ Music Awards and in three of her concert tours. It was the opening number of The Onyx Hotel Tour (2004), where she sang atop of a bus wearing a black catsuit; Spears also performed remixed versions of the song at The Circus Starring Britney Spears (2009) and the Femme Fatale Tour (2011). "Toxic" has been covered by artists such as Mark Ronson, A Static Lullaby and Ingrid Michaelson, and in television series Glee. The song has also appeared in feature films such as Knocked Up, You Again and television series Doctor Who. "Toxic" won Spears her first Grammy at the 2005 ceremony in the category of Best Dance Recording, while gaining her credibility amongst critics. The song has been included in lists by Pitchfork, NME and Rolling Stone as one of the best songs of the decade. It has been noted for redefining the sound of dance-pop music. Spears has named "Toxic" as her favorite song from her career.