U2 are an Irish rock band formed in Dublin in 1976. The group consists of Bono (lead vocals and rhythm guitar), the Edge (lead guitar, keyboards, and backing vocals), Adam Clayton (bass guitar), and Larry Mullen Jr. (drums and percussion). 

Initially rooted in post-punk, U2's musical style has evolved throughout their career, yet has maintained an anthemic quality built on Bono's expressive vocals and the Edge's chiming, effects-based guitar sounds. Bono's lyrics, often embellished with spiritual imagery, focus on personal and sociopolitical themes. 

Popular for their live performances, the group have staged several elaborate tours over their career.The band was formed when the members were teenaged pupils of Mount Temple Comprehensive School and had limited musical proficiency. Within four years, they signed with Island Records and released their debut album, Boy (1980). 

Works such as their first UK number-one album, War (1983), and singles "Sunday Bloody Sunday" and "Pride (In the Name of Love)" helped establish U2's reputation as a politically and socially conscious group. Their fourth album, The Unforgettable Fire (1984), was their first collaboration with producers Brian Eno and Daniel Lanois, whose influence resulted in a more abstract, ambient sound for the band. 

By the mid-1980s, U2 had become renowned globally for their live act, highlighted by their performance at Live Aid in 1985. 

Their fifth album, The Joshua Tree (1987), made them international stars and was their greatest critical and commercial success. One of the world's best-selling albums with 25 million copies sold, it produced the group's only number-one singles in the US to date: "With or Without You" and "I Still Haven't Found What I'm Looking For".

Facing creative stagnation and a backlash to their documentary and double album Rattle and Hum (1988), U2 reinvented themselves in the 1990s. Beginning with their acclaimed seventh album, Achtung Baby (1991), and the multimedia spectacle of the Zoo TV Tour, the band pursued a new musical direction influenced by alternative rock, electronic dance music, and industrial music, and they embraced a more ironic, flippant image. 

This experimentation continued on Zooropa (1993) and concluded with Pop (1997) and the PopMart Tour, which were mixed successes. U2 regained critical and commercial favour with the records All That You Can't Leave Behind (2000) and How to Dismantle an Atomic Bomb (2004), returning to a more conventional, mainstream sound. 

Although their twelfth album, No Line on the Horizon (2009), did not meet commercial expectations, the supporting U2 360° Tour of 2009–2011 set records for the highest-attended and highest-grossing concert tour,The U2 360° Tour was a worldwide concert tour by rock band U2.

Staged in support of the group's 2009 album No Line on the Horizon, the tour visited stadiums from 2009 through 2011. The concerts featured the band playing "in the round" on a circular stage, allowing the audience to surround them on all sides. 

To accommodate the stage configuration, a large four-legged structure nicknamed "The Claw" was built above the stage, with the sound system and a cylindrical, expanding video screen on top of it. At 164 feet (50 m) tall, it was the largest stage ever constructed.

U2 claimed that the tour would be "the first time a band has toured in stadiums with such a unique and original structure."[In an era of declining music sales, analysts expected U2 360° to be a major source of income for the band.

Every date of the tour sold out, many within minutes of tickets going on sale. To accommodate the time required to assemble and transport "The Claw" between tour dates, three separate stage structures were required on tour. The 360-degree production increased the capacity of venues by up to 25%, leading to attendance records at over 60 venues. 

Various themes were incorporated into the shows; portions of the concerts featured outer space themes, due to "The Claw's" resemblance to a spaceship. Pre-recorded messages from the International Space Station were displayed during the shows, as were sociopolitical statements from Desmond Tutu and Aung San Suu Kyi. 

The setlists were adjusted for each year of the tour; for the 2010 shows, unreleased songs were debuted live, while for 2011 legs, the group performed more 1990s songs to mark the 20th anniversary of the release of Achtung Baby.

Comprising three legs and 110 shows, the tour began on 30 June 2009 in Barcelona, Spain, and concluded on 30 July 2011 in Moncton, New Brunswick. It twice visited Europe and North America, while making stops in South America, Africa, and Oceania. The 2010 North American leg of the tour was postponed until the following year after lead vocalist Bono suffered a serious back injury. 

U2 won Billboard Touring Awards for Top Tour and Top Draw of 2010 and 2011, and for Top Boxscore at a single venue in 2009 for shows at Croke Park in Dublin. A 2009 show at the Rose Bowl in Pasadena, California was filmed for the concert video U2360° at the Rose Bowl and was streamed live over YouTube; the concert set a new US attendance record for a single headlining act.

The tour was generally well received by critics and fans. By its conclusion, U2 360° had set records for one of the highest-grossing concert tours at the time with $736 million in ticket sales, and for the highest-attended tour with over 7.3 million tickets sold.