Fun (stylized as fun. ) is an American alternative rock band based in New York City that was formed by Nate Ruess, formerly of The Format. After the 2008 breakup of The Format, Ruess formed Fun with Andrew Dost and Jack Antonoff of Anathallo and Steel Train respectively. Fun has released two albums: their debut Aim and Ignite in 2009 and their latest Some Nights in February 2012. The band is best known for its hit single "We Are Young" featuring Janelle Monáe.

"We Are Young" reached number one on the U. S.

Billboard Hot 100 and Digital Songs charts, becoming the first alternative song to top the Billboard Hot 100 chart since Coldplay's "Viva la Vida" in 2008. It also peaked at number one on the UK Singles Chart.

"Some Nights" was released as the album's second single in May 2012, peaking at number 11 on the Hot 100 chart, and becoming their second song to reach platinum status in the USA.