"When I Need You" is a popular song written by Albert Hammond and Carole Bayer Sager. It was first recorded by Hammond on his 1976 album When I Need You. Produced by Richard Perry, Leo Sayer's version made number 1 on the UK Singles Chart for two weeks in February 1977 after three of his earlier singles had stalled at number 2. A massive hit worldwide, it reached number 1 on the Billboard Hot 100 for a single week in May 1977; the song also went to number 1 on the Hot Adult Contemporary Tracks. He performed it on the second show of the third season of The Muppet Show.

The melody of the "hook" line, or chorus of "When I Need You" is identical to the part of the Leonard Cohen song "Famous Blue Raincoat," where the lyrics are as follows: "Jane came by with a lock of your hair, she said that you gave it to her that night that you planned to go clear." The melody of these lyrics matches the lyrics of "When I Need You" as follows: "(When I) need you, I just close my eyes and I'm with you, and all that I so want to give you, is only a heart beat away." This similarity raises the question of whether or not the composers of "When I Need You" were aware of the Leonard Cohen song "Famous Blue Raincoat" and whether or not they used the melody from the Leonard Cohen song deliberately.

The song was covered by Céline Dion, Luther Vandross, Perry Como, Rod Stewart (on his compilation album If We Fall in Love Tonight), Alpha Blondy, Brotherhood of Man, Julio Iglesias, Cliff Richard and Clay Aiken. A Spanish version of the song, "Si Me Amaras (If You Loved Me)," was covered by Lani Hall on her 1985 album, Es Fácil Amar. The Cantonese duet version, known as "For You, I'll Never Give Up," was covered by Gallen Lo and Flora Chan, as the theme song of Hong Kong drama Feminine Masculinityin 1999.

"When I Need You" is a promotional single from Céline Dion's Let's Talk About Lovealbum, released on September 7, 1998 in Brazil only.

After Céline Dion finished her Falling into You Tour in June 1997, she began to record her next English album. Dion and her manager and husband René Angélil wanted to include few cover versions on it. David Foster came up with the idea of recording Leo Sayer's hit "When I Need You." The song, recorded at Paramount Studios and Chartmaker Studios, was produced by Foster and included on Dion's Let's Talk About Lovealbum, released on November 15, 1997. Céline Dion performed this song during the Let's Talk About Love avec Julie SnyderCanadian TV show in late 1997.

After a string of successful singles like "My Heart Will Go On" and "Immortality," Sony Music Entertainment decided to release "When I Need You" as a promotional single in Brazil (September 1998). Two previous singles were very successful in Brazil. However, with no music video and no promotion "When I Need You" failed to repeat the success of Céline Dion earlier songs.

Authors of "When I Need You" worked with Dion also on several other songs. Albert Hammond wrote "Just Walk Away," included on The Colour of My Lovealbum (1993) and Carole Bayer Sager wrote "The Prayer," which became a part of These Are Special Times(1998).

Brazilian promotional CD single

On October 29, 2007, Cliff Richard released When I Need Youand reached number 38 on the UK Singles Chart. It is also one of the five new recordings featured in his latest album Love... The Album.