"I Miss You" is a song by British electronic music group Clean Bandit, featuring vocals from American singer and songwriter Julia Michaels. It was written by Michaels, Jack Patterson and Grace Chatto, with production handled by the latter two and Mark Ralph. The song was released to digital retailers on 26 October 2017, as the fourth single from Clean Bandit's second studio album, What Is Love? (2018).
On 16 October 2017, Clean Bandit first announced the song and its release date on social media, along with the single cover and a pre-order set up on streaming services. Shortly afterwards, Michaels revealed on Twitter that she "wrote ['I Miss You'] at the height of an emotional roller coaster. When I was stuck at the top, this flew out of me." The group posted the first snippet of the song on social media two days later, in which Michaels' layered voice can be heard "singing the melody over a piano piece". Michaels later confirmed via a tweet that she wrote the song while Jack Patterson was playing the piano. Chatto spoke to Billboard on the meaning behind the track, saying: "It's a simple song, about the unbelievable pain of breaking up with someone you love." She also regarded Justin Bieber's 2015 single "Sorry", a highly successful song co-written by Michaels, as one of her favourites of all time, calling working with Michaels "a real honour".