"Illusion" is a song by English singer Dua Lipa. It was released through Warner Records on 11 April 2024, as the third single from her third studio album, Radical Optimism (2024). A club and psychedelic-dance song containing 2000's dance-pop influences, it was written by Lipa along with Caroline Ailin, Tobias Jesso Jr., and its producers Danny L Harle and Kevin Parker. "Illusion" topped the US Dance/Electronic Songs chart and reached the top ten in the United Kingdom, Bulgaria, Croatia, Flanders, and the Commonwealth of Independent States.
In 2023, Dua Lipa announced that her third studio album would be releasing in 2024. She released the first single from the album, "Houdini", on 9 November 2023. She went on to release the second single, "Training Season", on 15 February 2024. On 13 March 2024, the singer announced the album, Radical Optimism, via an Instagram livestream; she confirmed its title, cover artwork and release date. The tracklist of the album was also revealed on the same day, with "Illusion" serving as the seventh track.
Lipa announced the release of "Illusion" as a single on 4 April 2024, via her social media accounts, along with its cover artwork and a 30-second snippet of the song. It was released on 11 April 2024, through Warner Records.
Julia Koscelnik of V praised the song, stating that it "stands out as perhaps one of Lipa's best songs, showcasing the artist at her strongest". El Hunt of Evening Standard gave the song 3 out of 5 stars; she criticised the opening verse due to its "odd phrasing" but praised the chorus.
"Illusion" debuted at number 9 on the UK Singles Chart on 19 April 2024, becoming the third consecutive top-ten single from Radical Optimism. It entered the US Billboard Hot 100 at number 43 on the chart issued for 27 April 2024, and charted for 18 weeks before departing. Elsewhere, especially in Europe and Latin America, the song reached the top ten in Belgium, Bulgaria, Croatia, Honduras, Japan, Turkey and Russia, top twenty in Portugal, Panama, Paraguay, Lebanon, Ireland, Greece and El Salvador, top thirty in Australia, Canada, Norway, Sweden and Switzerland, top forty in Denmark, France, The Netherlands, New Zealand and Spain and top fifty in Slovakia, Czech Republic and Nigeria.
The accompanying music video for "Illusion" was released alongside the song. It was directed by Tanu Muino and filmed at the Piscina Municipal de Montjuïc in Barcelona. Vogue Adria compared the music video to that for "Slow" (2003) by Kylie Minogue. Both videos feature the competition pool diving structure and surroundings of Piscina Municipal de Montjuïc against the backdrop of Barcelona.