Singer Mariah Carey is being sued for copyright infringement over her 1994 Christmas mega-hit, All I Want for Christmas is You.
Songwriter Andy Stone says he co-wrote a song with the same name five years earlier, arguing that Ms Carey exploited his "popularity" and "style".
Despite sharing a title, the two songs appear musically different, but Mr Stone claims Ms Carey caused confusion and did not ask for permission.
Ms Carey has not yet responded.
A must-have on any Christmas playlist, Mariah Carey's All I Want for Christmas is You is one of the best known Christmas records of all time.
Since appearing on the album Merry Christmas in 1994, it has topped the charts in several countries and by 2017 had reportedly earned Ms Carey more than $60m (£48m) in royalties.
The song has been streamed one billion times on Spotify.
In a recent memoir, Ms Carey admitted to composing "most of the song on a cheap little Casio keyboard".
Mr Stone, who performs under the name Vince Vance with the band Vince Vance and the Valiants, is claiming at least $20m (£16m) in damages.
The complaint says that Ms Carey, as well as her co-writer Walter Afanasieff and record label Sony Music Entertainment, have earned "undeserved profits" from the song, arguing that the defendants "knowingly, wilfully, and intentionally engaged in a campaign" to infringe copyright.
Mr Stone argues that he never gave permission for his song to be used for any purpose, including "the creation of a derivative work".
It is not clear why the legal challenge has only been made now, 28 years after Ms Carey's song was released.
The complaint says Mr Stone's lawyers first contacted Ms Carey and her co-defendants last year, but were "unable to come to any agreement".
It is not unusual for different songs to have the same name, and the United States Copyright Office lists 177 entries on its website under the title All I Want for Christmas is You.