She teamed up with Paul Epworth, who co-wrote and produced her massive hit Rolling In The Deep, to write the song which has the same title as the film.
She said: "I was a little hesitant at first to be involved with the theme song for Skyfall. There's a lot of instant spotlight and pressure when it comes to a Bond song. But I fell in love with the script and Paul had some great ideas for the track and it ended up being a bit of a no-brainer to do it in the end.
"It was also a lot of fun writing to a brief, something I've never done, which made it exciting. When we recorded the strings it was one of the proudest moments of my life. I'll be backcombing my hair when I'm 60 telling people I was a Bond girl back in the day, I'm sure."
The track, recorded at Abbey Road Studios in London with a 77-piece orchestra, will get its first play on the singer's website at 0.07am on Friday.
The film, again starring Daniel Craig as Bond, is to be given its premiere on October 26.