A dance song containing psychedelic and French house influences,[1][2] it was written by Lipa along with Caroline Ailin, Tobias Jesso Jr., and its producers Danny L Harle and Kevin Parker.

[5] On 13 March 2024, the singer announced the album, Radical Optimism, via an Instagram livestream; she confirmed its title, cover artwork and release date.

[7] 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.

[10] 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.

[15] The video featured a climbing structure based on human towers, a tradition in Catalan culture.