song: All I Want for Christmas Is You
artist: Mariah Carey
album: Merry Christmas (1994)
writers: Walter Afanasieff & Mariah Carey

all instruments: Walter Afanasieff
backing vocals: Kelly Price, Melonie Daniels, Shanrae Price

This song is estimated to rank 11 on the list of best-selling singles of all time, making it the 2nd best-selling Christmas single, exceeded only by ”White Christmas” by Bing Crosby (1942). It is Mariah Carey's biggest hit and has earned the two songwriters a total royalty income of an estimated $50 million since 1994; that is, roughly, $1 million each, every Christmas. The song's appearance in the romantic Christmas drama Love Actually (2003) also helped to elevate the song into the collective Christmas consciousness.
Be sure to check out this interview with writer and producer Walter Afanasieff explaining the origins of the song, as well as this amusing clip of Mariah Carey and other celebreties singing it on Carpool Karaoke with James Corden.