Taken from Carey's album 1994 Merry Christmas, the modern classic was originally held off the top spot by East 17's Stay Another Day.
However, it finally climbed to the summit this week, after being streamed 10.8 million times.
"Happy Christmas UK! We finally made it!" said Carey on hearing the news.
"We are keeping the Christmas spirit alive together despite how dismal the year's been.
