"You'll Never Know" is a popular song with music written by Harry Warren and the lyrics by Mack Gordon. The song is based on a poem written by a young Oklahoma war bride named Dorothy Fern Norris.

The song was introduced in the 1943 movie Hello, Frisco, Hello where it was sung by Alice Faye. The song won the 1943 Academy Award for Best Original Song, one of nine nominated songs that year. It was also performed by Faye in the 1944 film Four Jills in a Jeep.

The song is often credited as Faye's signature song. However, Faye never released a record of the ballad, and frequent later recordings of the song by other singers diminished her association with it.

It was recorded in 1943 by, among others, Frank Sinatra and Dick Haymes. The Haymes’ version was also a number one hit for four weeks on the Billboard and Harlem Hit Parade charts.

Sinatra recorded his version at his first recording session at Columbia as a solo artist. (He had recorded at Columbia in 1939 as a member of Harry James’s band.) It was arranged and conducted by Alec Wilder with the Bobby Tucker Singers providing accompaniment. Sinatra’s version charted for 16 weeks starting July 24 and spent two weeks at number 2.