U2 is an Irish rock band.
Achtung Baby ( [ pronˈɑːktuːŋ_ˈbeɪbiː ] ) is the seventh studio album by Irish rock band U2 . Pop is the ninth studio album by Irish rock band U2 . Songs of Innocence is the thirteenth studio album by Irish rock band U2 . The Joshua Tree is the fifth studio album by Irish rock band U2 . U2 . This experimentation continued through their ninth album , Pop ( 1997 ) , and the PopMart Tour , which were mixed successes .