"Un Día (One Day)" is a song by Colombian singer J Balvin, English-Albanian singer Dua Lipa, Puerto Rican rapper and singer Bad Bunny and Puerto Rican producer Tainy. Tainy produced the song, while he co-wrote it with Balvin, Lipa, Bad Bunny, Alejandro Borrero, Clarence Coffee Jr., Tory Lanez, and Ivanni Rodriguez. Universal Music Group released the song for digital download and streaming as a standalone single in various countries on July 23, 2020. It appears on J Balvin's second compilation extended play (EP), Summer Vacation (2020), his fifth studio album Jose (2021), and the reissue of Lipa's second studio album, Future Nostalgia: The Moonlight Edition (2021). A house, Latin pop, and reggaeton song with dream pop melodies and dancehall flairs, "Un Día (One Day)" lyrically talks about emotions of nostalgia and longing between two alienated romantic partners over a somber piano riff. Critics praised the song's fusion of each participating artist's musical styles. The song placed on best of 2020 year-end lists published by Billboard, Idolator and Rolling Stone. It was nominated for Best Pop Duo/Group Performance at the 63rd Annual Grammy Awards. The song reached the top 10 on the charts in various Central American countries, and received multi-platinum certifications in the United States, Mexico, and Spain. The black and white music video for "Un Día (One Day)", which was released on the same day as the song, features Úrsula Corberó dancing to it and contemplating a heartbreak. It was nominated for Best Music Video at the 46th People's Choice Awards. Lipa performed the song at her livestream concert Studio 2054, with Bad Bunny and J Balvin contributing their verses through a video.