"I'm Not in Love" is a song by the English band 10cc, written by band members Eric Stewart and Graham Gouldman. It is known for its innovative and distinctive backing track, composed mostly of multitracked vocals.

Released in the UK in May 1975 as the second single from the band's third album, The Original Soundtrack, it became the second of the group's three number-one singles in the UK between 1973 and 1978, topping the UK Singles Chart for two weeks. "I'm Not in Love" became the band's breakthrough hit outside the United Kingdom, topping the charts in Canada and Ireland as well as peaking within the top 10 of the charts in several other countries, including Australia, West Germany, New Zealand, Norway and the United States.

Written mostly by Stewart as a response to his wife's declaration that he did not tell her often enough that he loved her, "I'm Not in Love" was originally conceived as a bossa nova song played on guitars, but the other two members of the band, Kevin Godley and Lol Creme, were not impressed with the idea for the track and it was abandoned. However, after hearing members of their staff continue to sing the melody around their studio, Stewart persuaded the group to give the song another chance, to which Godley replied that for the song to work it needed to be radically changed, and suggested that the band should try to create a new version using just voices.

Stewart came up with the idea for the song after his wife, to whom he had been married for eight years at that point, asked him why he did not say "I love you" more often to her. Stewart said, "I had this crazy idea in my mind that repeating those words would somehow degrade the meaning, so I told her, 'Well, if I say every day "I love you, darling, I love you, blah, blah, blah", it's not gonna mean anything eventually'. That statement led me to try to figure out another way of saying it, and the result was that I chose to say 'I'm not in love with you', while subtly giving all the reasons throughout the song why I could never let go of this relationship."

Stewart wrote most of the melody and the lyrics on the guitar before taking it to the studio, where Gouldman offered to help him complete the song. Gouldman suggested some different chords for the melody, and also came up with the intro and the bridge section of the song. Stewart said that the pair spent two or three days writing the song, which at that point had a bossa nova rhythm and used principally guitars, before playing it to Godley and Creme. Stewart recorded a version with the other three members playing the song in the studio on traditional instruments – Creme on guitar, Gouldman on bass, and Godley on drums – but Godley and Creme disliked the song, particularly Godley, as Stewart later recalled: "He said, 'It's crap', and I said, 'Oh right, OK, have you got anything constructive to add to that? Can you suggest anything?' He said, 'No. It's not working, man. It's just crap, right? Chuck it.' And we did. We threw it away and we even erased it, so there's no tape of that bossa nova version."

Having abandoned "I'm Not in Love", Stewart and Gouldman turned their attention to the track "Une Nuit a Paris", which Godley and Creme had been working on and which would later become the opening track on The Original Soundtrack album. However, Stewart noticed that members of staff in the band's Strawberry Studios were still singing the melody of "I'm Not in Love", and this convinced him to ask the other members of the group to consider reviving the song. Godley was still skeptical, but came up with a radical idea, telling Stewart, "I tell you what, the only way that song is gonna work is if we totally fuck it up and we do it like nobody has ever recorded a thing before. Let's not use instruments. Let's try to do it all with voices." Although taken aback by the suggestion, Stewart and the others agreed to try Godley's idea and create "a wall of sound" of vocals that would form the focal point of the record.

Stewart spent three weeks recording Gouldman, Godley and Creme singing "ahhh" 16 times for each note of the chromatic scale, building up a "choir" of 48 voices for each note of the scale. The main problem facing the band was how to keep the vocal notes going for an infinite length of time, but Creme suggested that they could get around this issue by using tape loops. Stewart created loops of about 12 feet in length by feeding the loop at one end through the tape heads of the stereo recorder in the studio, and at the other end through a capstan roller fixed to the top of a microphone stand, and tensioned the tape. By creating long loops the 'blip' caused by the splice in each tape loop could be drowned out by the rest of the backing track, providing that the splice in each loop did not coincide with any of the others. Having created twelve tape loops, one for each of the 12 notes of the chromatic scale, Stewart played each loop through a separate channel of the mixing desk. This effectively turned the mixing desk into a musical instrument complete with all the notes of the chromatic scale, which the four members together then "played", fading up three or four channels at a time to create "chords" for the song's melody. Stewart put tape across the bottom of each channel so that it was impossible to completely fade down the tracks for each note, resulting in the constant background of vocals heard throughout the song. Composer and music theory professor Thomas MacFarlane considered the resulting "ethereal voices" with distorted synthesised effects a major influence on Billy Joel's hit ballad "Just the Way You Are", released two years later.

A basic guide track was recorded first in order to help create the melody using the vocals, but the proper instrumentation was added after the vocals had been recorded. In keeping with Godley's idea to focus on the voices, only a few instruments were used: a Fender Rhodes electric piano played by Stewart, a Gibson 335 electric guitar and a Rickenbacker 4001 bass guitar played by Gouldman for the rhythm melody, and a bass drum sound played by Godley on a Moog synthesiser which Creme had recently purchased and learned how to program. The drum sound was very soft and more akin to a heartbeat, in order not to overpower the rest of the track. Creme played piano during the bridge and the middle eight, where it replicated the melody of lyrics that had been discarded. The middle eight is also the only part of the song that contains a bass guitar line, played by Gouldman. A toy music box was recorded and double tracked out of phase for the middle eight and the outro.