The ReVe Festival: Day 1 (occasionally referred as Day 1) is the third special extended play and the tenth overall by South Korean girl group Red Velvet. Released on June 19, 2019, through SM Entertainment, the extended play served as the first installation of the group's The ReVe Festival trilogy, which was later followed by Day 2 and Finale. An electro-pop and dance-pop record, the EP contains six tracks that sees the group exploring new genres.[5] Its production was handled by various songwriters and production teams, including Caesar & Loui, Ollipop, Moonshine, Trinity Music, Ylva Dimberg, Cazzi Opeia, Ryan S. Jhun, amongst others.
Upon its release, Day 1 received mixed to positive reviews from critics, who were polarized over its experimental and genre-hopping nature.[6] It was commercially successful domestically, becoming their ninth chart-topper on the Gaon Album Chart. Its lead single, "Zimzalabim", additionally peaked at number 11 and 10 on the Gaon Digital Chart and World Digital Songs charts, respectively. To promote the release, Red Velvet embarked on their third concert tour, titled La Rouge, and included songs from the EP on its setlist.