"One" is a song by Irish rock band U2. It is the third track from their seventh album, Achtung Baby (1991), and it was released as the record's third single on 24 February 1992. During the album's recording sessions at Hansa Studios in Berlin, conflict arose between the band members over the direction of U2's sound and the quality of their material. Tensions almost prompted the band to break up until they achieved a breakthrough with the improvisation of "One"; the song was written after the band members were inspired by a chord progression that guitarist the Edge was playing in the studio. The lyrics, written by lead singer Bono, were inspired by the band members' fractured relationships and the German reunification. Although the lyrics ostensibly describe "disunity", they have been interpreted in other ways.

Laurence Joseph Mullen Jr. is an Irish musician, best known as the drummer and co-founder of the rock band U2. A member of the band since its inception, he has recorded 15 studio albums with U2. Mullen's distinctive, almost military drumming style developed from his playing martial beats in childhood marching bands.