Jacquie O'Sullivan (born 7 August 1960) is an English singer and songwriter, best known as a member of the pop group Bananarama from 1988 until 1991, replacing Siobhan Fahey, who left in early 1988. The line-up with O'Sullivan had UK top five hits with "I Want You Back" (1988) and a cover of The Beatles' "Help!" (1989), recorded with comedy duo French and Saunders for the charity Comic Relief. In 1989, O'Sullivan joined the group on their first world tour. Prior to Bananarama, O'Sullivan was the lead singer of the band Shillelagh Sisters.