William John Paul `` Liam '' Gallagher ( born 21 September 1972 ) is an English musician and songwriter best known as a singer in the rock band Oasis . William John Paul `` Liam '' Gallagher ( born 21 September 1972 ) is an English musician and singer-songwriter , the frontman formerly of the 1990s Britpop band Oasis and currently of the band Beady Eye .