"Fallin'" is a song recorded, written, and produced by American R&B-soul singer–songwriter Alicia Keys for her debut album, Songs in A Minor(2001). Released to radio and music video outlets in 2001, it is generally considered her signature song. "Fallin'" became Keys' first number-one single in the United States and her first top five hit in several countries. It is also Keys' second biggest single to date after 2007's "No One". "Fallin'" won three Grammy Awards in 2002, including Song of the Year, Best R&B Song, and Best Female R&B Vocal Performance. In 2009 the single was named the 29th most successful song of the 2000s, on the BillboardHot 100 Songs of the Decade. Rolling Stoneranked it number sixty-two on their Top 100 Songs of the 2000s decade. The song charted at 413 in Blendermagazine's 500 Greatest Songs Since You Were Born.

Keys described the song as being a strong representative of who she was as an artist. She explained that the song was about the "ins and outs" of being in a relationship. She went on to say, "Sometimes, you're completely head-over-heels in love with someone, and sometimes you can't stand that person. You fall in and out, sometimes it goes back and forth, and that's just what relationships are about."

Although it is regarded as Keys' signature song, it almost did not become her single. Before she joined J Records, Keys had signed a recording contract with Sony's Columbia Records. Sony felt that Keys should sing more mainstream-accessible material written by others, while she insisted upon recording her own compositions. As a result, Keys' recording career remained in limbo for two years. Bored and with free time on her hands because of Sony's lack of interest in her, Keys decided to put her time to good use and began to write a song. Instantly, arpeggios hit her, and she became inspired with the chords that would define "Fallin'". She quickly composed lyrics basing the tune on the emotions she faced during one of her first serious romantic relationships.

As Keys was still in artistic limbo, the song was originally not meant for her; Sony intended to have Kim Scott, a child prodigy signed to their label, record "Fallin'". Keys became uneasy over the matter, as she wanted to record the song herself, but could not because Sony was not focusing on her career. At first Keys had surrendered the piece to Scott willingly, but later changed her mind, and Scott did not record it. Clive Davis, a former Columbia executive then at Arista Records, heard about Keys and was impressed with her artistry. After Davis started a label of his own, J Records, he bought out Keys' Sony contract and signed her to his label.

Once at J Records, Keys began working on her debut album, Songs in A Minor. Unlike Sony, J Records did not mind Keys recording her own compositions, and encouraged her to do so. When it was time for a first single to be chosen, "Girlfriend", a song Keys had worked on with Jermaine Dupri while at Columbia, was considered, but Keys and other executives agreed that "Fallin'" would be the best choice.

"Fallin'" is a gospel-influenced song. It begins with piano and basic drum programming, then proportionally builds up to a crescendo. The record also features a violin performance of the pizzicato and legato strings by Miri Ben-Ari. Keys' collaborator Kerry "Krucial" Brothers provides the song's digital programming. The song samples 1966's "It's a Man's Man's Man's World" by James Brown. The song is written in the key of E minor.

The song was one of the most critically acclaimed songs of the year. Barry Walters of Rolling Stonecompared Keys performance in the song to an Aretha Franklin vibe. Sal Cinquemani of Slant Magazine complimented Keys' voice, saying it was a "restrained vocal that never permeates the track's tight arrangement". Christian Ward of NMEalluded to the song being emotional, saying it will make the listener "weep 'til you're a dribbling, snotty wreck". Simon Price of The Independentcalled the song Keys' breakthrough song. Stephen Thomas Erlewine of Allmusic pointed out the lack of depth in the song, saying it "doesn't have much body to it", which he felt was "a testament to Keys' skills as a musician". The song was listed at number four hundred and thirteen on Blendermagazine's list of The 500 Greatest Songs Since You Were Born and at number four in The Village Voice 's 2001 Pazz & Jop critics' poll. "Fallin'" was banned from many Australian Idolauditions due to its popularity.

"Fallin'" was released in April 2001 as Keys' debut single, amidst considerable promotion and praise from Davis and J Records. "Fallin'" peaked at number one on the U.S. Hot 100 and Hot R&B/Hip-Hop Songs charts and remained there for six and four weeks, respectively. It also reached the top position in the Netherlands, Belgium, and New Zealand as well as the top five in the United Kingdom, France, Italy, Germany, Austria, Switzerland, Norway, and Ireland and the top ten in Sweden and Australia. A remix of the song, featuring Busta Rhymes and Rampage from the Flipmode Squad (also at that time signed to J Records), included on the British edition of her album, reimagines the song as a hip hop-flavored dance song. Since its release, "Fallin'" has become a popular standard for contestants in the reality television series American Idol.

As one of the most critically acclaimed singles of 2001, "Fallin'" was nominated for several awards. "Fallin'" connected well with NARAS as the song was nominated in 2002 for four Grammy Awards: Song of the Year, Record of the Year, Best Female R&B Vocal Performance, and Best R&B Song. It ended up winning Song of the Year, Best Female R&B Vocal Performance, and Best R&B Song (Record of the Year was awarded to U2's "Walk On").

At the 2001 Billboard Music Awards, "Fallin'" was nominated for the Hot 100 Single of the Year; however, it lost the award to Lifehouse's "Hanging by a Moment". The song was also nominated for Outstanding Song and Outstanding Music Video at the 2002 NAACP Image Awards; it did not win in either category.

The music video for "Fallin'", directed by Chris Robinson. Unlike most other contemporary R&B videos, the video for "Fallin'" was a low-key clip with no dancing. The video opens with a radio playing "Girlfriend", where Keys is sitting at a piano. The plot has Keys traveling to a prison to visit her incarcerated boyfriend. The plot is continued in the video for Keys' next single, "A Woman's Worth", which explores what happens when Keys' boyfriend is released and, with her help, adjusts back to regular life. Keys said in an interview that she was supposed to be the one incarcerated, and her boyfriend was visiting her.