"Beautiful Day" is a song by Irish rock band U2. It is the first track on their tenth studio album, All That You Can't Leave Behind (2000), and was released as the album's lead single on 9 October 2000. The song was a commercial success, helping launch the album to multi-platinum status, and is one of U2's biggest hits to date.

Like many tracks from All That You Can't Leave Behind, "Beautiful Day" harkens back to the group's past sound. The tone of the Edge's guitar was a subject of debate among the band members, as they disagreed on whether he should use a sound similar to that from their early career in the 1980s. The band's lead vocalist Bono explained that the upbeat track is about losing everything but still finding joy in what one has.

The song received positive reviews, and it became the band's 14th number-one single on the Irish Singles Chart. Outside Ireland, "Beautiful Day" topped the charts in Australia, Canada, Finland, Italy, the Netherlands, Norway, Portugal, Spain and the United Kingdom, and peaked within the top ten of the charts in Austria, Belgium, Germany, New Zealand, Sweden and Switzerland. "Beautiful Day" also peaked at number 21 on the Billboard Hot 100 in the United States, the band's highest position since "Discothèque" in 1997.

In 2001, the song won three Grammy Awards for Song of the Year, Record of the Year, and Best Rock Performance by a Duo or Group with Vocal at the 43rd Annual Grammy Awards ceremony. The group has played "Beautiful Day" at every one of their concerts since the song's live debut on the Elevation Tour in 2001.

"Beautiful Day" originated from recording sessions held by U2 in a small room at Hanover Quay Studio in Dublin in the winter of 1999. In its earliest permutation, "Beautiful Day" was a different song called "Always", which was later released as a B-side. The song's genesis came from a chord sequence that lead vocalist Bono composed and that guitarist the Edge subsequently adapted. The group worked on the song for several days in the studio, but were unable to make much progress with it. The Edge said, "As a straight rock song, it was pretty ho-hum." Co-producer Daniel Lanois said: "the sound of it was a bit stuck in the barroom, and as usual our expectations were high. We wanted to feel the future and not just the past."

Co-producer Brian Eno was frustrated with the lack of progress on the song, and early one morning, he and Lanois arrived in the studio before U2 to prepare some musical ideas. Eno created a rhythm on a drum machine, over which he added a piano part and synthesised strings. Lanois played a guitar part on a Fender Telecaster that was a third above the root of the Edge's guitar sequence, providing what he described as a "choral quality, like harmony singing". The producers' ideas proved to be musically inspiring to the band when they arrived and resumed work on the song. Lanois described the Edge's resulting guitar playing as "sounding like shattered, splintered metal coming at you like a meteor storm". Near the end of a 20-minute jam of the song, Bono sang, "It's a beautiful day, don't let it get away". After taking a lunch break, the producers thought that Bono's impromptu vocal from the outro could be made into the song's chorus. They quickly edited the vocal part into earlier sections of the jam, turning it into what would be the chorus of "Beautiful Day".

Before leaving the studio one day, the Edge listened to the chorus vocals, and thinking they sounded bare, he picked up a microphone and improvised a backing vocal, singing a high fifth. At the same time, Lanois harmonised a lower doo-wop style vocal that he described as similar to those in "The Lion Sleeps Tonight". Their voices were then doubled and processed by Eno. The Edge called the backing vocals a "beautiful counterpoint" to Bono's singing and "the final key element that the song needed".

During the recording process for the All That You Can't Leave Behind album, the band decided to distance themselves from their 1990s experimentation with electronic dance music in favour of a "return to the traditional U2 sound". At the same time, the band was looking for a more forward looking sound. This led to debate amongst the band when the Edge was playing the song on his Gibson Explorer guitar with a tone used in much of their early material up to their 1983 album War. Bono was particularly resistant to the guitar tone the Edge was playing with, but the Edge ultimately won the disagreement. As he explained, "It was because we were coming up with some innovative music that I felt a license to use some signature guitar sounds."