"Swear It Again" is a song by Irish boy band Westlife, released as the first single from their debut album Westlife. It peaked at number one in the UK Singles Chart for two weeks in May 1999. It moved to 182,000 units in the first two weeks of its release and spent 13 weeks on the charts. This made it the first of fourteen UK number-one singles. To date, it is Westlife's only single to have charted in the U.S., peaking at number 20 and number 75 on the Billboard Hot 100 Year End Chart in 2000. The song was performed live on Miss Teen USA 2000. The single has sold over 365,000 copies to date in the UK and the US and also achieved gold status there.
"Swear It Again" is notable for being, along with "Flying Without Wings", one of the first two songs that Steve Mac wrote for both Westlife and Simon Cowell. The success of the two tracks led to Mac becoming Cowell's first choice producer and songwriter. The song's B-side, "Forever", was a significant choice because it was the song - as originally recorded by Damage - that first alerted Cowell to the talent of Steve Mac and then led to the producer working with Westlife.
The British video features the band in a mini theatre, singing on a stage fitted with lighting panel flooring while facing a screen with black and white videos of their studio recording process. This version was directed by Wayne Isham and aired in May 1999. The United States video features the band at a car wash and subsequently washing a white car. This version was directed by Nigel Dick and aired in June 2000.