Nate Ruess (born February 26, 1982 in Iowa City, Iowa, United States) is an American singer-songwriter and musician.

In 2001, at the age of 19, he launched the band The Format with his longtime best friend, Sam Means. The Format was his first musical endeavor to gain widespread attention. The Format lasted until 2008.

In 2008, Ruess started a new band with Jack Antonoff of Steel Train and Andrew Dost of Anathallo. The band was called fun.. With fun.