"All I Want for Christmas Is You" is a song by American singer-songwriter Mariah Carey from her fourth studio album and first holiday album, Merry Christmas (1994). She wrote and produced the song with Walter Afanasieff. It was released as the lead single from the album on October 29, 1994, by Columbia Records. The track is an uptempo love song that includes bell chimes, backing vocals, and synthesizers. It has received critical acclaim, with The New Yorker describing it as "one of the few worthy modern additions to the holiday canon". The song has become a Christmas standard, with a significant rise in popularity every December.

The song was a success when first released, reaching number six on the Billboard Hot Adult Contemporary chart in the United States and number two in the United Kingdom and Japan. The advent of music streaming has led to renewed success for the single, which now annually re-enters charts worldwide in the weeks before Christmas and has reached number one in over 30 countries. The single has broken the record for the longest gap between release and reaching number one in both the United States and the United Kingdom, 25 and 26 years respectively. It is the best-selling Christmas song of all time in the US. It is certified Diamond in Australia, Canada, Sweden, and the US. The song has sold over 16 million copies worldwide, making it one of the best-selling digital singles of all time. As of 2023, the Associated Press estimated the song's royalty earnings at $100 million. That same year, the song was selected by the Library of Congress for inclusion in the National Recording Registry.

Following the success of her 1993 album Music Box, Carey and her management at Columbia Records—including Carey's then-husband, Tommy Mottola, head of Columbia's parent label Sony Music Entertainment—began planning further projects. The group discussed recording a Christmas album, but hesitated, as such albums were typically released when artists' careers are waning. Carey's songwriting partner of over four years, Walter Afanasieff, said in 2015: "Back then, you didn't have a lot of artists with Christmas albums. It wasn't a known science at all back then, and there was nobody who did new, big Christmas songs. So we were going to release it as kind of an everyday, 'Hey, you know, we're putting out a Christmas album. No big deal.'"

After Mottola persisted, Carey and Afanasieff began writing and composing songs for Merry Christmas in June 1994. When recording "All I Want for Christmas Is You" that August, Carey had Christmas decorations set up in the studio. She later called this "an amazing recording session, like no other".

Initially, Afanasieff admitted that he was puzzled and "blanched" as to where Carey wanted to take the melody and vocal scales, though she was "adamant" in her direction for the song. In an interview with Billboard, Afanasieff described the type of relationship he and Carey shared in the studio and as songwriters:

It was always the same sort of system with us. We would write the nucleus of the song, the melody primary music, and then some of the words were there as we finished writing it. I started playing some rock 'n' roll piano and started boogie woogie-ing my left hand, and that inspired Mariah to come up with the melodic [Sings.] 'I don't want a lot for Christmas.' And then we started singing and playing around with this rock 'n' roll boogie song, which immediately came out to be the nucleus of what would end up being 'All I Want For Christmas Is You.' That one went very quickly: It was an easier song to write than some of the other ones. It was very formulaic, not a lot of chord changes. I tried to make it a little more unique, putting in some special chords that you really don't hear a lot of, which made it unique and special.

Then for the next week or two Mariah would call me and say, 'What do you think about this bit?' We would talk a little bit until she got the lyrics all nicely coordinated and done. And then we just waited until the sessions began, which were in the summer of '94 where we got together in New York and started recording. And that's when we first hear her at the microphone singing, and the rest is history.

Afanasieff flew back to California, where he finished the song's programming and production. Originally, he had a live band play the drums and other instruments with the thought of giving it a more raw and affective sound. He was unhappy with the results of the recording and subsequently scrapped the effort and used his original, personal arrangement and programmed all the instruments heard on the song (with the exception of the background vocals) including the piano, effects, drums and triangle. While Carey continued writing material in her rented home in The Hamptons, Afanasieff completed the song's programming and awaited to rendezvous with her a final time in order to layer and harmonize the background vocals.