Lady GaGa, Tony Bennett duet on 'The Lady is a Tramp': Listen now
The pair recorded the Rodgers and Hart show tune - originally penned in 1937 - for Bennett's forthcoming album Duets II. The song became a jazz standard and has previously been recorded by Frank Sinatra, Ella Fitzgerald, Sammy Davis Jr and Shirley Bassey.
Bennett described GaGa as "warm, friendly and sweet" in a recent interview, saying that he was "thrilled" to hear that the Born This Way musician wanted to work with him because she is "in such great demand".
He has also described her as the most talented artist he has ever met.
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Bennett has also collaborated with Michael Bublé and Mariah Carey on Duets II.
His version of 'Body and Soul' - recorded with the late Amy Winehouse - was released as a single on Wednesday to mark what would have been her 28th birthday.
All proceeds from the single release will go to the Amy Winehouse Foundation, which was also officially launched on Wednesday.
Watch Lady GaGa wishing Tony Bennett a happy 85th birthday below: