"What Is Life" is a song by the English rock musician George Harrison from his 1970 triple album All Things Must Pass. In many countries, it was issued as the second single from the album, in February 1971, becoming a top-ten hit in the United States, Canada and elsewhere, and topping singles charts in Australia and Switzerland. In the United Kingdom, "What Is Life" appeared as the B-side to "My Sweet Lord", which was the best-selling single there of 1971. Harrison's backing musicians on the song include Eric Clapton and the entire Delaney & Bonnie and Friends band, with whom he had toured during the final months of the Beatles. Harrison co-produced the recording with Phil Spector, whose Wall of Sound production also employed a prominent string arrangement by John Barham and multiple acoustic rhythm guitars, played by Harrison's fellow Apple Records signings Badfinger.

An uptempo soul tune, "What Is Life" is one of several Harrison love songs that appear to be directed at both a woman and a deity. Harrison wrote the song in 1969 and originally intended it as a track for his friend and Apple protégé Billy Preston to record. Built around a descending guitar riff, it is one of Harrison's most popular compositions and was a regular inclusion in his live performances. Rolling Stone magazine has variously described it as a "classic" and an "exultant song of surrender".

"What Is Life" has appeared in the soundtrack for feature films such as Goodfellas (1990), Patch Adams (1998), Big Daddy (1999), Away We Go (2009), This Is 40 (2012) and Instant Family (2018). Harrison's original recording was included on the compilations The Best of George Harrison and Let It Roll, and live versions appear on his album Live in Japan (1992) and in Martin Scorsese's 2011 documentary George Harrison: Living in the Material World. In 1972, Olivia Newton-John had a UK hit with her version of the song. Ronnie Aldrich, the Ventures and Shawn Mullins are among the other artists who have covered the track.

Even before his temporary departure from the Beatles in January 1969 (documented in the song "Wah-Wah"), their Apple Records label was an "emancipating force" for Harrison from the creative restrictions imposed on him within the band, according to his musical biographer, Simon Leng. In his article on All Things Must Pass for Mojo magazine, John Harris has written of Harrison's journey as a solo artist beginning in November 1968 – when he spent time in Woodstock with Bob Dylan and the Band – and incorporating a series of other collaborations through the following eighteen months, including various Apple projects and a support role on Delaney & Bonnie and Friends' brief European tour. One of these projects, carried out intermittently from April to July 1969, was his production of That's the Way God Planned It, an album by Billy Preston, whom Harrison had met during the Beatles' Hamburg years and had recently been recruited to guest on the band's troubled Get Back sessions. It was while driving up to a Preston session in London from his home in Esher, Surrey, that Harrison came up with the song "What Is Life".

In his autobiography, I, Me, Mine, Harrison describes it as having been written "very quickly" and recalls that he thought it would be a perfect, "catchy pop song" for Preston to record. He adds that he changed his mind once he arrived at Olympic Studios and found Preston working on more typical material – or "playing his funky stuff". Rather than attempt it with the Beatles during the band's concurrent Abbey Road sessions, Harrison stockpiled "What Is Life" with his many other unused songs from the period, including "All Things Must Pass", "Let It Down", "I'd Have You Anytime" and "Run of the Mill". He revisited it a year later, after completing work on Preston's second Apple album, Encouraging Words.

Harrison biographer Simon Leng describes "What Is Life" as "Motown-spiced" and a comparatively rare example of its composer's willingness to embrace the role of "entertainer" in his songwriting. The song is defined by Harrison's descending guitar riff, which also serves as the motif for the chorus. Author Alan Clayson describes "What Is Life" as a seemingly "lovey-dovey pop song" that "craftily renewed the simplistic tonic-to-dominant riff cliché".

The lyrics have a universal quality, being both simple and uplifting. Their meaning has caused some debate among biographers and music critics, as to whether "What Is Life" should be viewed as a straightforward love song – perhaps a "lovingly crafted paean" to Harrison's wife Pattie Boyd, in Clayson's description – or a devotional song like many of Harrison's compositions. Ian Inglis writes that the song title suggests a "philosophical debate about the meaning of life", yet its rendering as "what is my life" in the choruses "reshapes [the meaning] completely".

Theologian Dale Allison finds no religious content in "What Is Life" but comments that the "failure of words to express feelings" implied in the opening line ("What I feel, I can't say") is a recurring theme in Harrison's spiritual songs. Joshua Greene, another religious academic, identifies the song as part of its parent album's "intimately detailed account of a spiritual journey": where "Awaiting on You All" shows Harrison "convinced of his union with God", "What Is Life" reveals him to be "uncertain that he deserved such divine favor". According to musicologist Thomas MacFarlane, the ambiguity in the lyrics suggests a connection between spiritual and physical love.